75 Eldorado Conv. need body

I have a 75 eldorado that I bought from Chicago area. It has alot of rust
around the bottom of the fenders and floor panel.  The question I have is,
can the hole entire rear fender be taken off and replaced or do I have to
get someone to cut it out and weld sheetmetal or something like that.  The
rust is eating though the paint and I have alot of holes thoughout the
car.  I can just about replace every thing else, such as the hood and
front fenders and doors.

Or does anybody have a donor car that the body is in good condition with
no motor or top that I can buy? This car is in good running condition, but
I can't paint it. Help?