Welcome to irv2 longlyclan
You will have to remove everything off the bottom of the chair, mounting plates and post.You need help removing, start by placing back of chair thru door opening first than turn chair out thru door opening. Also if you remove cabinet doors it may give you some manevering space. Most large coaches didn't have spare tires, going to Alaska it would be a good idea to have one. You will have to give up some space under in one of your compartments. They do make a tire carrier that mounts on your towing bar, not sure how much time you have to order one.
Your serial# should be on a sheet in one of your cabinets with a brake down of appliences serial#'s.