I'm new here, but as I'm in the business I'll add my two cents. Like many others have said I would schedule this for a whole day, while hoping to be done in 4 to 5 hours. I've only changed a few vent fans since usually just a new motor fixes the problem. The ones I have changed have been huge pains in my butt! So while the concept is simply, it never seems to go that way. On the electrical box thing I'm on his side. I don't have a huge truck and needing an electrical box is pretty rare for a handyman. Remember we specialize in small repairs and have to be prepared for a wide range of things. While I try to be prepared I can't stock everything. I'll agree with you on the door, he should be able to hang a slab door.