I paid £8.75 for a full set of O rings for my Rebas – via a recommendation on this thread. I assume the guy also sells the equivalent for Revs, it may even be exactly the same set.
As others have said, the oil will do many services. Its a bit nerve-wracking the first time you take your forks to bits, but when you’ve done it once you’ll find it very simple the next time. Just follow the instructions in the Rockshox service manual. Nice and slowly, with a cup of tea, making sure you don’t miss any steps and remember the order you took things apart in.
Do invest in some circlip pliers if you’re opening up the internals though, mine cost less than a tenner.
And the best way to avoid stanchion wear is to do the small lube service every few months. That’s even easier, and completely unnecessary to send them away just for that.