Start by checking out ebay, Craigslist, RV Trader, etc., and having a look at what comparable trailers are going for. The Ebay "completed" listings are especially valuable, as you can see what the actual sales price was. Now, does your hail damaged trailer have a salvage or rebuilt title? Knock of 25% if so. If not, did your insurance company write you a check for the hail damage? If so, subtract that amount from whatever you come to as a "market" price.
Of all the "new" stuff you list, I would say that it makes little difference in the value of the trailer. When someone buys a trailer, the expectation is that everything works. They take deductions for everything that does not. The only thing that I would say should count as a "bonus," and drive up your asking price slightly is the solar panels--and then you still have to gamble that your customer cares to have solar.
The hail damage is potentially your biggest negative. The front of the endcap looks like it has some dramatic dents, you may have to go with a large deduction (again...25% may be appropriate). You can always start high, and see what people are willing to pay. It is easier to drop your price than it is to raise it.