If that trailer is in good shape...that is requiring no major paint stripping, rust or dent repair and has good rubber...that is a fairly good deal. I put that and more in my M416 when I did a total rebuild several years ago.
Depending on what your plans are these are typical costs you might experience:
Sand blasting ~$250 to $350
Body work - ??????
Paint (materials only) ~ $100 to $250
Shocks ~ $50
Bearings, races and seals ~ $30 to $50
Misc suspension replacement parts ~ $100
Electrical <$40
Misc fasteners (bolts, nuts and washers) $0 to $150
Theres more, but I am starting to cry...
I completely disassembled, blasted, repainted and reassembled using NOS and new parts. Mine cost me a bit more than most.