It's not rocket science, as said "No leaks, and No oils or greases....anywhere! " that also means cleaning the torch that my be covered in oil etc from just having sat around.
One thing to considder.... When things go wrong they go wrong FAST and the person using the torch is holding on to the part that most likely will go. Take it from some one who has been there when something went wrong with O2. I would NOT do work on a customers torches unless 1) you have the training and the paper work to prove it. 2) your liability insurance WILL cover it!
I am trained by several dive equipment mfgs to service regulators and such. I am also trained to service these things for 100% high pressure oxygen. Even with the training, I would NEVER work on someone else's equipment on my own due to the HUGE liability that I would take on in the event something would god forbid happen. When I work for a shop, the shops liability covers me in the event something goes wrong. It doesn't even have to be my fault, bad oring for the mfg, cust does something stupid ( I have see this dozens of times), with the liability coverage I am protected. I did what was required, dotted the I's cross the T's and jumped thru the hoops they wanted.
Just keep this in mind ahead of time. Good luck.