I had a 1998 F150 with the 4.6L. I recently sold it to my nephew. I crown rustproofed mine anually from new. I recommend the following.
Have it oil sprayed. Judging by the cancer (rust) already eating the body, I suspect your brake and fuel lines.
Inspect the tie rods ends (inner and outer), and the ball joints (upper and lower). I had to replace all of mine @120K
New wires,plugs,and coils may be needed. The engine may appear to be running great, but if any of these components are
suspect, the engines' computer will compensate for these and lower your MPG.
K&N filter did little for me. Stick with the stock filter.
I installed a dual high flow exhaust which offered litle performance, but it sure sounds cool.
I wouldn't bother with the body work, just drive the piss out of it for a couple of years and save your money for gas and a newer F150.
Are those snow tires? You may need to buy some rubber.
Good luck, and congats on your ride.