Depends entirely on your mechanical ability. I've never taken a bicycle to a shop for somebody else to work on.

A bicycle is a pretty simple machine but the devil is in the details. Some parts, like the left pedal and right side of the bottom bracket have left hand threads. Some parts have to be screwed more tightly than I would do if left entirely to my own judgement. Some, mostly higher end bikes, have parts that can be damaged by screwing them too tightly.