1999 Sienna, 250,000 miles, $3,600. Bad idea?

Hi there...

I need a vehicle for doing some light hauling here and there, not a daily driver or nationwide vacations or anything
like that. I'm actually going to use it to move from an apartment into a house 18 miles away, and after that just keep it around to use for anytime I need to haul stuff that won't fit in a car, like buying furniture and whatnot. And I think a minivan would come in handier than a pickup truck, and get better gas mileage and be easier to drive than a full size van. My budget is $2000-4000.

After doing some minivan research and a few test drives I like the Sienna the best, but they're pretty hard to come by in this price range, around this area anyway.

I found a 1999 Sienna XLE with 250,000 miles, though the seller says he replaced the engine with a 160,000 mile wreck salvage engine. (also new tires) He's asking $3,600 for it. KBB, Edmunds, NADA, and Autoblog all price them around $3300-ish for that mileage and I'll see what I can work it down to. I test drove it, and I really liked it; it handled well, accelerated effortlessly, no transmission issues, steady temperature, no pull to either side, all of the interior gizmos worked. My mechanic friend says the engine looks good. So it seems to have been well maintained. I got an InstaVIN report and all it said was that it's had three owners, so I'm still in the dark about service records. The seller doesn't have any either.

The only thing holding me back is the mileage, and also the fact that it's an XLE so I'm paying a premium for luxuries I don't need. All the other minivans in this price range seem to have one chronic problem or another, or are comparatively unreliable. So I'm wondering how a 250,000 mile Sienna with a good reputation for reliability holds up to a lower mileage minivan with a worse reputation. I don't mind having to replace a worn out part here and there but I don't want a full restoration project either.

Do you think buying this would be a mistake?