I'd keep the Bonneville. 1000 bucks well spent could bring her back into nice shape, with your buddy'* help.
Of course, if you REALLY want the Jeep, get the Jeep. Ask yourself why you REALLY want it. I read an article about consumerism once, and American Marketing has us, as a society, trained to become UNhappy with everything in our lives roughly every 21/2 years. Thats cars, houses, possesions, even relationships.
I think it will be cheaper, in the long run, to keep what you have. 97 isnt really old.