I won't give links as they can be a bit "adult"! The sites can be a bit scary if piercing isn't your thing :shock:
Body Modification Ezine is an excellent information resource, but not for the faint-hearted! and a UK site Body Jewellery Shop dot com has lots of info and shows you all the goodies you can buy. Not as scary as BME!
Hygiene is the key. If you wouldn't be prepared to eat your dinner off the floor, don't get your piercing done there. Research before you go shopping for your piercer. Ask you pierced mates where they got theirs done.
A long term health condition is no barrier to body modification, I don't intend to let my diabetes stop me from getting another tattoo when I'm ready (I have 2, both custom pieces).
Aftercare is everything and if you are unwell or are having any issues with healing DON'T DO IT!
The horror stories are related to poor hygiene and aftercare.