First, you will need have it gone through and have the entire airframe inspected, the engines pulled, broken down and replace many, many parts....Ahh, just junk 'em and buy new engines, probably as cheap. Then assemble your new aircraft. Ready to fly? Hang on a sec!! There is more! Since ejection seats are verboten in civilian avaiation, you will need to come up with new seats, oxygen system (assuming they use LOX) and lots of avionics (can't use military, not FAA approved).Then there is the FAA inspection and flight certification. I don't know how that would be done.
What am I forgetting? Oh, yeah! You have to be typed for the F-18, and since the one offered is likely a single seater, finding a tandem F-18 to train and someone to sign off on your rating will be a challenge. Probably have to go to a foreign government to get that. Then there is on going maintainence...
Cost? Probably $10-15 million over and above the cost of the jet. I dunno...