NEWB WITH QUESTIONS PLEASE HELP

[CHARICTER]

hi everyone! I've been looking through the forum the past week, tring to gather any information i could find. dont want to post up what has already been posted. pretty sure these are questions that have been ask before so sorry. im looking to buy a (e53) x5 going for the 4.6is. just wondering do they really have that many problems? is it fearly easy to work on? did they get better after 04? do the cons out weigh the pros? and any information that you think would be useful?

also im debating between the x5 and a e46 m3 smg witch would be better?

or

should i stay with my 323is and mod it?

sorry again for the newb questions. and thank you for your time.