I would hesitate to put a tattoo directly over scar tissue. The skin there behaves a little funny. Just FYI.

As for how intricate you can get it, I would spend some time asking people with tattoos you like where they got them done. When you decide to check someone out, go to their shop and flip through their portfolio... NOT the big posters on the wall or in the flippies, but they should have a genuine photo album with stuff they themselves have inked onto people. Look for patterns: does this artist do lots of fine linework? Good with shading? Leans towards tribals or full color or photorealistic? Get to know someone with a style similar to what you're after.

A good artist should be able to draw up something for you, probably with a deposit. If you only have a vague idea of what you want, you can work together with this person to have the perfect design.

You'll know it when you see it. It's the art that you realize that you can't live your life without. It's the stained glass on the temple of your new body.

-- gnat! (lotsa ink, no regrets)