A good way to cheaply and easily start doing your own service is to buy an older reg off ebay or Craigslist, then dissamble, clean, lube and reassemble it. While this is not a complete rebuild by any means since you don't replace any of the parts, the process is exactly the same. Find a source of parts (most of the parts are common orings or can be purchased at vintage double hose ) and you can complete the rebuild. Most of the older piston regs are very similar- SP MK-2/3, USD Aquaruis, many Dacors and a host of others. For diaphgram regs, the older Conshelfs are exactly the same internally as the later Titans and Legends. The later 70s Mares MR-12 are very similar to the Conshelfs inside and make nice regs as well. The second stages of all of them are basically the same as the low end second stages sold today....although IMO better built. Many of these regs can be had for under $20 and you can end up with a good backup reg in the process. With the exception of a one tool I can think of (and it's just nice to have) none of these regs require any reg specific tools although circlip pliers and oring picks are maybe not in everyones tool kit.