Parts to go first.....hopefully none!
Ego5 is a great marker, I've got an rarely used spare which works first time, every time.
Just look after it - oil the bolt and rammer and keep them clean. Maintenance on the HPR and LPR is simple. In my experience, there isn't too much to go wrong.
Worth looking at Youtube - a few Ego5 maintenance videos on there (even the original planet eclipse ones).
Make sure you use the correct lubricants as directed.
Cheers