Transmission Worries and Tire Concerns

I am a happy owner of a '01 S2K (45k miles). I am having trouble with the transmission. I am completely locked out of 6th gear and have been for a couple of months now. The rest of the gears work fine, but I can't get in to the last one. I also notice that when I am driving and let off of the accelerator, I get a rather loud rumble (steady) from the engine bay. I can't believe this is normal. Perhaps it is related to the tranny trouble. Any one have an idea? I was going to take it to the dealer, but they want $500 just to look at it. I am also driving in the winter with snow, sleet, freezing rain, etc. What are some of the better tires to get for winter driving? I have heard Bridgestone Blizzaks are good or Dunlop Wintersport M2/3. Do I just need to purchase a set for the rears? Any help is much appreciated.

Matt

your synchro? you sure you don't have any trouble shiting in 1st?