What I'm going to say may sound like anal motherhood but I think that you might want to consider this from a different perspective, and I applaud you for being prudent in at least asking the questions.
It has been said a few times in different forums on this board that the challenge for fairly new divers diving in "advanced" dive sites isn't so much that there is a strong current, that it is deep, that it is rough or what have you. It is, instead, having to deal with some or all of these external stress factors, while at the same time worrying perhaps about air consumption, buoyancy, equalizing, kicking, figuring out the equipment, etc. - things that you get much better at over time and with more dives. It is under these stressful circumstances that a diver can sometimes become overloaded and overwhelmed.
So while it is true that the pass dives can be easy and you will most likely come out of the dives quite fine and thrilled, sometimes they can be challenging. Also consider how much more you might enjoy dives like these if you spend more time looking at what's out there and less time looking at your gages, for example.
Here are some of the elements of these pass dives that can add to the degree of difficulty:
1. you will most likely have to make a negative entry. As best as I can recall, there is no getting in, bobbing at the surface until everyone is ready and then descending. The current is usually strongest at the surface, so hanging too long near the surface means getting blown too far into the pass.
2. you may need to make a quick descent to the bottom and latch on to something. At most of these passes, the heaviest shark action is right at the mouth. Only at the southern pass in Fakarava are the sharks at their heaviest concentration inside the pass. If the current is strong and a diver is slow in descending - equalizing issues, for example - again, he or she may get blown well into the pass and separated from the group.
3. if the current is strong, the dive guide may choose to drop in a little further out into the blue to give divers more time to descend. When you backflip into the blue, especially if you have never done it before, it can get a bit disorienting to see all blue and have nothing to reference against. As an aside, if you find yourself in this predicament, calm yourself down - breathe - and try to locate the dive guide: he will always know which way is up or down and which way to go.
4. The depth at the mouth of the passes is over 100 ft. When I dove these, we usually stayed there for a few minutes before letting go to start the drift. If you hover in mid-water and are not latched to something, you would have to be kicking a lot (and using a lot of air) to maintain position, and if the current is more than let's say 1 knot, you will drift away into the pass anyway.
By now, you are probably thinking that being well inside the pass is not good. Not true. As I said earlier, there are lots of Grey Reef sharks inside the southern pass in Fakarava. You might also see two types of Black Tips. The reef wall on your right as you drift inwards is exquisite. Midway into the Fakarava northern pass, there is an area that Serge at Fakarava Diving Center (highly recommended, BTW) calls The Valley. The amount of fish here is unbelievable and you can also see small groups of Grey Reefs patrolling. In Tiputa Pass in Rangiroa, there are these things that look like WWII dug-out trenches at the bottom of the pass - you duck into these trenches and can watch all kinds of stuff drifting above: sharks, mantas and dolphins.
5. it can sometimes be mighty choppy at and just inside the mouth of these passes. Dolphins love to go surfing on these waves, specially at Tiputa Pass. You don't normally surface here - usually you drift further into the lagoon where it is pretty nice and calm. But what if you got separated or were low on air?
6. about the current: I've seen easy and I've seen intimidating as in rip your mask and reg off.
I know that I have painted a pretty gloomy picture here, but when assessing the risk of any situation, you also have to look at worst case. Taken one at a time, a fairly new diver can manage. Add several of the above together and it could be challenging even to divers with more experienced.
With that said, I understand this being a once-in-a-lifetime trip and your wanting to get the most out of it. Hopefully you will love it so much that you will want to make many future returns.
Suggestions: for starters, I'd say be totally honest with the dive operator about your experience level so that they can plan your dives accordingly and so that they can look out for you. Altho it is their responsibility to lead a safe dive, safety ultimately starts with you and diving within your capabilities.
Second, it might be wise to spend the first few days doing only the reefs on the outside at either side of the mouth of the pass and maybe even the lagoon dives to build up a little more confidence before asking the dive operator about doing the passes.
The reefs on the outside are gradual sloping walls as opposed to vertical walls with no bottom, so you can pick a depth you are comfortable with and maintain it. If there is any current out there, it'd be very light and the dive guide would have you drift with it anyway. As already mentioned by others, these are beautiful dives in of themselves with lots to see.
Have a great time.
