GT performance do some really nice shock overhauls but much like you I find it more satisfying to do stuff myself. I have rebuilt my SP, F3 and RS250 shock and really quite straight forward if you have the tools required. The only really specialised/expensive tooling is the nitrogen charging equipment, I have access to a nitrogen rig at work but most motocross dealers should be able to recharge a shock for very little cost.
What type of shock do you have? I'm presuming its an SP remote reservoir type. The next question is what are you aiming to achieve, a full restoration or just an oil change and re gas?
I should have some pictures of my rebuild, I will have a look and start posting some up. If you havent done so already have a look on you tube, lots of videos of shock rebuilds on there.