Problems, one possibly big

[85Silverado]

Ok...my truck is soild for the most part, mechanically anyways, but the back of the bed is rusted through and the tailgate on the passenger side pretty much hangs loose where the hinge is at the bottom, i know that can be replaced or fixed with some fancy welding but my main concern is the floor in the cab. The rocker panels are pretty much gone on the drivers side and i can see movement in the floor on the hump that the seat sits on on the edge and am worried about the seat falling down that way. What's the best way to go about fixing that or will i need a new cab? Thanks for any and all info.