Any idea how much it would cost to fix this/how hard it is to fix by myself?

 

Your best bet is to get another pass. front door and reapier the rear.

 

And how much would that cost?

 

Depends on where you get it from, I got one for my GF's 96 Accord for $60 from a junkyard in G.A. The only thing that it didn't have were the window and door panel.

 

Skin the front door, repair the rear. If the shell is too damage you will need to replace the door. Call a honda dealership for a price on the skin. Isn't all that hard to repair yourself if you know your way around it, if you have no experience at all, it'll be a bit tougher, but can be done.