To answer your last question, no you should not install the tires yourself unless you have the correct tools and a balancing machine. Its not expensive to get them done at a shop.
When I used to live in the US I found Discount Tire were pretty good, not sure if you have them local to you. Or try Tirerack.com
As far as brands go, I have used Pirelli Asymetrico, Dunlop SP9000 and Continental to good effect, we get about the same amount of rain as you guys
so you need something with good channels and water shedding properties rather than a larger tread block. These three I have found to be great both wet and dry. I tried Kuhmo's and did not like them at all, but I know other people do so I guess its down to personal choice.
Cheers