I will say I very biased towards this boat, I have a 99 Speedster since new. To me it's hands down the best boat under 18' that Seadoo ever made(especially in Yellow). The interior is not shot, those seats are supposed to look like that, they sorta have a splash pattern on them. Now if they are hard and cracked, that's another story, then you will need to chat with the guy that Lou gave you the link for. The driveshaft, easy fix it's the same one as a 96 XP and many other models and can be had cheap and easy used, check the splines on the impeller if that is the end that stripped. The reverse cable--bound to break at any time. I take good care of my boat and all of a sudden in the driveway operating the gate lever mine snapped up by the controls. It's missing all the red caps for the control levers (esthetics only but I noticed it in the pics). If all you need are those 2 parts you can be fixed for probably less than $200. The trailer needs a fender (unless he has it) and should be bolted down through the foot pad on the fender--the original mounting sucked. I ripped one partially off just pulling out of the ramp a little too quickly. I would offer less but $1800 is down right insulting, especially if he starts it up for you. But if your comfortable starting there by all means do it, cheaper is always better in the long run. There will be standard things that will need to be done, like cleaning carbs and rebuilding them--right there is about $300 with gasket kits and needle and seats, then another $40 in carb gaskets, the boats use a thicker gasket than the ski's do, but a thin one will work.**Very important---> Check the rubber bellows around the exhaust where it exits the hull, they dry rot every couple of years (about 5 years), they are no longer available and you will be fighting me for them on Ebay, LOL I snag them when I can on there. They will leak water right into the hull, guys seal them with silicone and what not-- that's not my bag. I would park the boat before I risked it filling with water. Depending on how mechanically inclined you are if you picked it up for $2500 and had to put 2 SBT engines in it, plus fix all the other stuff you'll be right at "advertised" book value--not necessarily what you would get if you had to dump it. Again, I'm very comfortable with this boat so there is not one repair that I can't handle, if you need to pay someone to do this work, then you might be in over your head. Being you first boat you will have a learning curve but we can help you out here on the forum to get you the knowledge to repair it quickly and get the job done right! Also, consider this a 4 person boat as the bow seat is the bouncy seat. I have thrown a grown man off that seat, yet it's my 9 year old boys favorite seat in the boat. Best of luck, ultimately the choice is your's to jump off the bridge, just be prepared to get in deep with fixing and spending!
Here's the reverse cable, if you can get it at the dealer the OEM one is only $5 more PART#204170058
http://www.shopsbt.com/mm5/merchant.mvc?Screen=PROD&Product_Code=27-2107R