I have 1999 ford PC (23') which I bought (used) last year. I was aware about the bottom of the side entry door problem- will not shut tight. I can see a 2" gap along the bottom of the door, when it is closed. By being a brand new RV/owner I have no clue how to fix this, can the door be replaced. If so, where can I buy a new door that will match my rig and where can get it installed. Help!