You should post questions in the proper forum, which would be the 2-stroke PWC, I'll see if I can help. The problem with putting your questions in the wrong forum is a lot of guys won't look twice and you won't get the help you need.
1. The starter, unless the starter you have is not OEM you are generally better off rebuilding the starter that you have. You can do it yourself for about $30.00 or take it to a local shop and have it rebuilt. Do not buy a cheap $60.00 Chinese starter off EBay.
2. I'm not sure what to tell you on the gas gauges. Do you have separate gauges? They are usually part of the multi-function gauge, but in either case try contacting minnetonka4me on this forum, he has lots of good used parts and reasonable prices. I know you said you had water in the gauge, but usually when the fuel gauge quits, shows empty with a red light, its the fuel float, if you need to replace the float get the newer molded type.
3. Grips, this is just personal preference, but I like the ODI grips, they're a little larger and I like the feel, plus they "smile" at you when you are riding.
Lou