I rebuilt a 2004 model for a gentleman a couple years ago. It was a rental ski that had 442 hours on it and had put a hole through the aft piston. There are 6 crank bearings and there is no way you are getting to 4 of them without specialized tools. The whole engine has to be completely disassembled and then the crank is pressed apart using a hydraulic press and special crank web separation tools.
The point is this: The ski complete, as is condition, is worth about $500. This means that it isn't torn apart, no parts missing, the exhaust is laying in the hull, etc.
It will cost you $400-$500 just to have the crank rebuilt by a professional shop that specializes in that. I had mine done by RAS Racing out in California (if they are still around). Their online site was jetskimechanic.com
I know some people save a few bucks by buying a rebuilt crank from SBT in Florida, but I'm not a huge fan of the mass-remanufacturer. Call me old fashioned, but I like knowing that one person is doing the work and doing it with precision.
If your budget really is $1200, I wish you good luck. For that money you can get a running ski, but it's not likely that it's going to run for long. Just my past experience with the old 2 strokes. However, I can say that Kawasaki builds a stout tripple. It won't be a speed demon like some of these new Sea-Doos but if you rebuild one right, and do the required yearly maintenance it deserves, it will give you years of reliable service.