1999 2 dr 4 X4 Auto transmisson
 

I'm thinking about buying this, actually, a trade for my 98 Ford Windstar. Their asking price is $3000. Mine is $3300. So I looked at this today and took it for a short test drive. When accelorating, it was slow to shift up and I found that if I took my foot off the gas for a moment, then it shifted. Seller has had it since 2003. It has 240,000-some kms on it and has been parked since last winter. They told me they replaced the alternator but apparently, that is the only "major" work they've done on it. When I mentioned the shifting problem, they said "well, it's been sitting awhile". Could this really cause the problem I experienced? Also they said it's hard to get out of 4 wheel. They said you have to stop, back up, and then go forward for it to release. Is this a major problem that will need work or is it OK with it like that?
Thanks for your responses. I really appreciate it.