'86 TRX250R/Fourtrax won't start

I am new to this site, and have had my quad sitting in my garage for years. yes, YEARS!! My killswitch just slides to and fro, like it doesn't lock into position in either "on" or "off". Does that need to be replaced, or could it possibly work just sliding like that? so i have no experience working on bikes, I assume I need to dump the gas, change the spark and see if it starts? also My tires are flat, I have new ones but I'm not sure how to remove the old ones from the rim... Help please!! anyone have an idea how much this bike might be worth both 1. in this condition, and 2. if it was fixed up a bit

I'm VERY BROKE right now, looking to spend the least amount possible just to get it to run, and I really need to sell it so please give any advice you can!

http://www.hondaatvforums.net/gallery/showgallery.php?cat=501