hi pompomfairy, i got mine done about 2 months ago, and have had no problems, i didnt find that it hurt - though i have to say that when i went back to the piercer to get the bar changed it hurt like hell!!
Just make sure you go to a nice clean piercing place and should be no problems :-)
to clean it swish some warm salt water in your mouth after everything you eat and 1st thing on a morning and last thing at night. - the swelling on mine went down after about 3 or 4 days. for these days i found i could only eat ice cream & mash potato!
If i were you id see if the piercer will change the bar for you when its healed (to a shorted one - this is probably after about a week), because i have found that even just putting the ball on the top is very very tricky!!
The only bad thing ive come across with mine is that sometimes ill bite down really hard on it when im eating - and that hurts!!
just go for it!! :-)
let us know how it goes!!
em x