I can't tell you what do do, but FWIW, I will share our experience. Two years ago we bought a 1996 motorhome. We were looking around and hadn't planned to buy quite so soon, but this one sort of fell into our laps. For reasons that are too long to go into here, we got a very good deal on a unit in great condition.
But if you're buying used, particularly of the vintage you're looking at, you have to be very careful and know a decent amount about motorhomes to make certain you don't get burned. There's a lot more to a used MH than buying a used car. How's the engine? Transmission? How are the appliances? Does it leak? Does the generator work? Are the plumbing and electrical in working order? Anything the vintage you're looking at will probably need some work, at least minor, even if it's in great shape. Although ours was in great condition, there were still several things that needed repair. Fortunately DH and I are quite handy and we've fixed most of it ourselves, but if you aren't handy or inclined, be aware that those costs will fall on you. And even if everything is absolutely perfect when you buy it, if it's older, things will start to go wrong eventually. That's just the nature of the beast.
It can be difficult to find someone to work on motorhomes, as well. Make certain you have someone nearby who can service both the chassis and the appliances and coach. Otherwise you'll end up very frustrated the first time something needs fixing.
Then there are the maintenance costs. If you look a little ways down, you'll see I'm spending $1000 on six new tires this week. Tires need to be replaced every 5-7 years. Don't forget oil changes (we do this ourselves, but you may not want to), state inspections (if required where you live), cleaning costs, generator maintenance, etc. Also don't forget that you'll most likely have to buy propane ever so often to run your heater and fridge. Then there are the smaller things like holding tank chemicals, hoses, filters, special cleaners for the roof and awnings, etc., etc.. When we got the MH and started setting it up, we spent close to $1000 in the first few weeks we had it, just getting everything we needed to outfit it and set it up. Walmart loved us!!!!
A motorhome is certainly not the least expensive way to vacation, especially not in the beginning when you're setting it up and getting the things you need (and some you don't but really, really want). We find that campgrounds are cheaper than hotels, though and that we can travel more than we used to because (finally) the costs are averaging out. We've gotten the unit to the point where it doesn't need as much work (money going out) and that we can spend tat money on actual travel now. So we are now (sort of) starting to realize some savings on our travel, although the ongoing maintenance eats into that somewhat. And don't forget gas. While I don't know what gas will do in the future, it's wise to give this area some thought. Ours has a 75 gallon tank. If gas hits $4/gallon like some are predicting, it will cost me $300 to fill that puppy up. It's still cheaper than flying most places for me, but it definitely eats into any "savings" we might be making by camping.
The ongoing maintenance isn't cheap either. It's probably better than owning a boat ("a hole in the water into which you throw money") but not by much. If you're just getting out of debt, this might be a bit much for you right now. There are a lot of things that "come up" with a motorhome (particularly an older unit) and if you don't have money set aside for them, you can find yourself pretty quickly racking up the credit cards or, worse, parking the unit in the yard because you can't afford the upkeep. You don't say whether you have any extra money saved up that would cover these things, so I don't know for sure what your situation is. I would recommend making certain that you can deal with all the things that will come up without going back into debt. Do a lot of research and ask a lot of questions.
All that said, however, we love it and will probably never go back. I see a future of gradually upgrading our motorhomes and if I'm lucky by the time I'm 65 maybe I'll be in one of those really nice coaches. We don't have a big group, just us two and a dog, but we love that we can bring her when we go somewhere. We love having our own "stuff" and our own beds. We love having our own place. When it rains, we're not stuck in a hotel room with nothing to do. We have DVD's, games, the computer, and a full kitchen. No bed bugs. It's nice to be able to get away from home without really leaving home.
I might suggest that for your WDW trip, you look into renting an RV. This isn't cheap either, but it's cheaper than buying and the maintenance isn't your problem. You could drive it to WDW, stop at the Grand Canyon and visit New York. Spending this time with an RV would help you learn if you like it, what you really want in an RV, and whether you really want to own one. Then if you do want one, you'll have a better idea of what you want and need and maybe you'll have more money put away to deal with the maintenance and stuff. This is just my experience and opinion, so some of it may apply to you and some may not. But it's all I've got.