Is your window itself thats damaged or is it just the siding? If its the window, its hard to tell if it would leak water unless you actually take it out and can see daylight in the damaged spot. If its in the siding, you could fill it with some sort of kitchen/bath or exterior silicone for a temporary fix until the weather gets warmer and you can take it back to the dealer. The only way to fix dents in the aluminum is to replace the panel. The aluminum skin is used by most manufacturers, so it should be available even though Sunline is out of business (at least for now!!!). Hopefully the dealer you bought it from would be willing to replace the panel and not just patch it somehow.
2007 T-286SR Cherry/Granola, #6236, original owner, current mileage: 9473.8 (as of 6/18/21)
1997 T-2653 Blue Denim, #5471
1979 12 1/2' MC, Beige & Avocado, #4639
Past Sunlines: '97 T-2653 #5089, '94 T-2251, '86 T-1550, '94 T-2363, '98 T-270SR