I think the most challenging part is being careful when disassembling the motor; several shim washers, try to maybe make notes and stick them to scotch tape, sketch washers then fan blades, more washers then armature then more washers. A cheap set of calipers & you could note the thickness of the washers. Work over a big plastic pin when you pull it apart so none fall onto floor. Check the length of the brushes, and note curvature worn by the armature, if reinstalled differently, they may spark a lot until they reseat. I'm going too long here, sorry. A motor rewinder might be better than an "electrician"
Good luck!