1: Is the suit to big for me? or would that have anything to do with this problem? I am 5'10" about 160lbs.
Specifically which model of Whites drysuit do you own? I'm about the same height/weight as you. I fit into the Whites Fusion L/XL size. For a Whites Nexus/Catalyst drysuit, I'd fit into a medium. If you have a Nexus or Catalyst drysuit, an XL suit will definitely be too big for you. The fit might be so poor that it could be rather dangerous -- too many places for gas pockets to be created which will complicate maintaining proper horizontal trim and could inhibit venting.
To make sure that a drysuit fits, you
need to try it on. If you don't know how a drysuit should fit, you need to find someone to help you. Any experienced drysuit diver or dive shop that sells drysuits should be able to help you. When purchasing a drysuit (used or new), the most important thing to ensure is proper fit. It's a safety and comfort issue.
The drysuit hole through which a diver sticks his head is typically a standard size. Generally speaking, a neck seal of the appropriate size should be able to be installed on any drysuit so that the suit can "fit" people with fat, skinny, or "normal"-sized necks.
2: Did he cut the neck seal to short?
I have no idea. I'm going to assume that a
latex neck seal is installed on your drysuit. FWIW, there are other materials that neck seals can be made of (neoprene, silicone, etc.).
First of all, you need to make sure that the latex neck seal installed has a "fit range" that matches the size of your neck. Not every latex neck seal is one size fits all. For example, I take a "medium" size Viking-brand bellows-style seal.
Secondly, you need to trim the ring appropriately. It helps to work slowly, use a sharp cutting tool (rotary cutter, razor blade, scissors), and err on the side of leaving it slightly tight. Dangerously "too tight" refers to a fit that causes bulging neck veins, restricted bloodflow to the head, and diminished/labored/difficulty breathing. You should be able to don your neck seal and comfortably sit on your couch for an hour. Watch a baseball/basketball/hockey/football game. As you wear it, you should forget that it's even on. Something else to keep in mind is that over time, a latex seal will relax a little. That's why I recommend trimming it to be "slightly tight." Otherwise, 6 months down the road, your neck seal might start to leak.
I hope that the guy at your local shop had you don the neck seal to ensure proper fit. There's no such thing as "eye-balling" how much to trim down a latex neck seal. The fitting process usually consists of trimming one ring, trying it on, trimming another ring, trying it on again, etc.
3: My experience level is lacking and I need a class? (Already signed up for one)
This is a good idea. You should be learning to operate a drysuit from someone who knows how. That person can be an instructor, mentor, or experienced drysuit buddy. A formal drysuit course should teach you how to recover from a feet-first ascent, how to trim neck/wrist seals, how to make sure that your drysuit fits, how best to manage the drysuit bubble (during ascents, in particular), the importance of proper horizontal trim, how/when to add gas to your BCD rather than your drysuit, how your undergarment + drysuit combo affects weighting requirements, and how to store/maintain your drysuit.
Good luck with learning how to use your drysuit. Hopefully, it is the right size for you and the learning curve won't be too steep. If it's not the right size, sell it off and buy something that fits.
FWIW, becoming truly comfortable in a drysuit will take lots of dives. I thought I had it down after a couple of dives. 10 dives later, I felt like I had more control. 25 dives after that, I was feeling quite comfortable. 50 dives later,
much more comfortable. With 100+ drysuit dives, I didn't have to think at all about operating the suit. Now I can't imagine diving in SoCal water without one. When I go on warm water dive vacations, during initial descent, I try to hit the drysuit inflater button in the center of my chest. I look pretty silly since I'm usually diving a 3mm wetsuit. YMMV.
