I have been in the diving business for over 27 years. If you want access to parts to DIY, then I would suggest that you develop a relationship with your LDS. For one thing don't come to them with an attitude "I can fix my car, I can fix my regulator". Politically incorrect. As in any trade you need a mentor/teacher.
Another point, What does one do if you don't have the tools? They don't rent them. Try to make them? You may scratch and ruin the finish on your regulator to prove a point, I have seen people try to open a regulator with pliers. You can buy the tools,it will add up to a fortune, might as well bring your regulator in to get worked on. Unless you are going into business to fix regulators, it is not worth the investment. you are better off buying another tankfor more bottom time.
Getting back to the subject of this forum, parts. I will gladly sell you parts if you can show that you are competent and don't act like a jerk. I would even let you use my tools, but remember I am letting you into my house, don't s#$t on it.
If people would just realize that I am willing to scratch your back if you do mine when it itches too, people could be get a long with each other better.