conf file access on host server

hi, i'm a relative new comer to php and was wondering if someone could give me some advice on hosting. specifically, access to my own conf file, and whether this is entirely necessary. Does not having access to your own conf limit what you can do in php in any way? also, if you have compiler access on the server, does that mean you can install your own libraries, etc? I'm currently looking at www.gradwell.com and they seem pretty good. any advice? Thanks, Diane Mulberry