just a quick piggyback...
1) if you can patch the foam, you can get replacement seat vinyl extremely well priced at seadooupholstery.com I've used Keith for his kit on my challenger and I was quite pleased with the quality, and the price was fantastic. He's a member here out of Lauderdale, good quality and ships fast.
2) The hull cleans up extremely well with some effort, but very little cost was involved, it took me a couple of weekends to clean up my 96 Challenger (lots of square footage) but with some soft scrub,compound/wet-sanding/buff & wax it went from a chalky faded dull mess to a real nice finish and it probably took me about 15 hours of effort, which wasn't bad considering how it looked beforehand. So don't be afraid of the hull, it will look great if you just put in some time. Those boats still sell in the $4,000 range when clean & running so you will get good value out of it even if you grow tired of it over the summer.
3) most parts that are not the shifters or electronics are quite reasonable to replace, latches (ebay $10), cup holders (walmart $2), but cables were pricey $130ish? and turf can cost $200 ( I got lucky and found my turf for $100 on ebay) most of the engine parts are just standard 787 and cheap.
4) not a fast boat..and quite sluggish, but it is a good basic run around for a small family, handles chop fairly well, but its best on smooth wate, but won't be that bad in mild chop, just not in heavy chop. One nice advantage of this hull is that you can run in quite shallow waters where other boats can't go, we've been on a challenger quite a ways up the peace river where its pretty shallow in the fall and the boat was able to go wherever the ski's could, so we were pleasantly surprised.