I will second what John told you. A Polaris dealer should provide an estimate for you on their repair order. However, if it comes to a repair/replace question, you need to know what the insurance company considers that threshold. Typically, an insurance company will total a vehicle out when the repairs equal or exceed 80% of the current market value. My suggestion to you is do a little research. The reason I say that is typically dealers will not charge for estimates if they get the job for repair. If it totals out, they may want to charge you an hour labor to prepare that estimate. I suspect this is going to be really close to totaling out. To take every action you can to prevent having to pay for an estimate, you should look up the parts that you can see that are damaged and get a total on that. I can tell you an off the cuff guess on labor based on what you presented, would be about 3 hrs. One thing to keep in mind when a shop quotes, or gets paid for labor by an insurance company, take in to consideration overlapping labor. that means if they need to take the handle bars off to replace the front fenders, they will not get full labor as if the ATV came in just for a handle bar exchange. They would pick up a little bit of labor because they would have to replace grips or switches. One other thing you mentioned was re-painting. Again, typically nothing is repainted as a repair, unlike the automotive industry. Typically they just replace the damaged parts, such as your dented fuel tank. This would be another question you could ask your insurance company too.
I just took a quick look at a Polaris parts catalog on line and it doesn't look like the fenders or seat are available any longer. Add the fuel tank to that list too. It is looking like all the major parts you need are not available. How your insurance company handles that is strictly up to them.
The sad reality is since it is a 2003, it isn't going to take much in damages to total the vehicle out. I looked it up on Kelly Blue Books and they put a retail value of $900 in excellent condition.
Hopefully that helps.
If you have any more questions, feel free to ask. If I would advise you, I would call your insurance company armed with the information given here and just see what they have to say. I wish you luck.