Oversea-
If you want to work on your regs to save money or time, go to a good service shop and pay the man whatever he wants and thank him, because he has probably saved your life. People trying to save money usually cut corners. A person with this mentality should never touch a reg when its out of his mouth. However, if you are mechanically inclined, and understand how a regulator works and what the parts do, go ahead and give it a shot. There are no secrets or magic needed to service regs, just some knowledge of accepted practices and common sense. Learn everything you can about them before working on them. Example: If you don't know the difference between a static and dynamic o-ring, or if you are planning on using your brand new, expensive, top-of-the-line, really nice stainless steel o-ring picks, study some more. 1st stages are very demanding in terms of inspection, cleaning, and assembly, mainly do to the high pressures involved. Buy some older regs on ebay and get busy. I didn't dive in OW with the first reg I worked on, but I dive-tested each one in my pool. As my confidence and experience grew, I began doing all of my service work. I'm the type of person that needs to know first-hand that my equipment is assembled and working correctly, and I won't take anyone's word for it, since it is my life that is on the line. As scubaroo pointed out, ScubaTools is a great source for service tools, Christolube 111, and test equipment. Scubastore.com has service kits for several brands of regs and they will sell to you direct. Even though they are located in Spain, your order will arrive within a week. I use them a lot. If you need some technical info, send me your email address. I have the complete Poseidon manual, SP Mk14, Zeagle, Oceanic, and several others. Although the Poseidon 2nd stage is different than most other 2nds (it has a diaphragm actuated, servo assisted valve. The upstream valve is the reason why the LP hose has a pressure relief valve at the 2nd stage end) it will help you learn some of the common servicing and cleaning techniques, including: don't use steel picks to remove o-rings because you will scratch the sealing surface and ruin the part. ;-)
oversea:
I am a hands on type of person. I like to get into things, repair, make my own etc. and have been considering doing my own rebuilds. I found what seems to be a decent book that covers a broad range of regs and their functions. My main regs are a set of sp s600 mk25 in which I don't want to start out playing with, but I do have a set of older poseidon regs that desperately need some work and thought they'd be a good start. Can anyone tell me a good place to buy the parts kits?