how much is VERY expensive? i got this as a gift so i paid nothing for it.
Off the top of my head, you'll be paying $60-$100 (or more) at a local Apeks dealer if you bought each of those parts a la carte. If Apeks does have a kit with all of the necessary parts included, you might pay closer to the bottom end of that range.
You really should speak to a local Aqualung/Suunto/Apeks dealer. Any authorized dealer can order the parts. Don't be surprised, however, if the LDS employee gives you a blank stare in response to your question. Your request is a little out of the ordinary, from the perspective of the LDS. The employee will have to pull out the latest Aqualung parts catalog, verify the part numbers needed, and place a call to the parts warehouse. Don't be surprised if the parts will take weeks to arrive or if some of them are on backorder. Your LDS may also charge you for shipping of the parts and installation (if not done as part of an overhaul). After all that, I'd be shocked if the whole sh-bang will end up costing you less than $100.
Alternatively, you could purchase one of the environmentally-sealed HOG first stages for $125-$150. It would come with a warranty, but you'd have to attach all your regs and tune them on your own. That's not a bad thing to learn how to do, though.
You could also go with a Zeagle first stage that's environmentally sealed. The 50-D and DS-V are excellent, sealed balanced diaphragm regs rated for cold water use.
Yet another thing to consider is whether your
second stages are rated for cold water use. Apeks regs typically have a heat exchanger which is designed to prevent the second stage from freeflowing in cold water. Once again, this part can be added to the ATX20 or XTX20, but it's going to be a special order part.
As has already been mentioned, if you're diving water that in the high 40s (°F) or warmer, then you should be able to use your unsealed first stage with proper tuning and cold water practices. Aqualung/Apeks officially places the cut-off between warm and cold water diving at 50°F.
