I have gone there several times. One time the service was OK. The other not so good. I took it there to have the gas gauge fixed (only read 7/8 of a tank when you fill it up). They said they fixed it, but then next fillup, it was still wrong. Brought it back, they said they fixed it, but again it was still broken. I wound up giving up on them successfully fixing it.
As for setting an appointment, you just have to bring your car in. I don't think they do appointments there.