Hi,
Having removal here too. It's a slow process and painful, although it gets less painful as the ink fades. Mind has always healed quickly after each session. It's a long process - the longer you leave it in between sessions, the better, as your body needs time to break down the 'shattered' ink and get rid of it, so you wouldn't expect to be having sessions more frequently than every 8 weeks or so.
The easiest colour to remove is black ink, and the fresher the tattoo, the better it responds. They have to use different frequencies for different colours and some (not sure which) are particularly hard to shift. Mine was about 10 years old when I started to have the sessions, and she was unsure how well it would respond. You might have trouble shifting a 15 year old one.
Mine is a hand sized tattoo on my outer thigh, black ink only. I go to a dermatologist in Central London to have it removed and am paying £200 per session. I've had probably 7 sessions over the course of about 2 years. It is still visible, although much faded. Some areas have pretty much disappeared. I am white as a sheet though, so even the palest mark shows up on me!
To be honest, I am not sure where to go from here. I might try a couple more sessions. Apparently it is 'responding well'. A friend had a tattoo 'corrected' where the woman went over it in flesh-coloured ink. Now it is so much paler, this might be worth looking into. I haven't discussed it with anyone yet, so I don't know if it is a realistic solution or not.
At the end of the day the only way you will know whether it will shift is to try a session.
Good luck! And take painkillers half an hour or so before each session - ot does make a difference!