get the model with the 21" wheel package, and you won't have to worry.
stock wheels and tires, least for the 21" package are actually really good. rims are pretty light, and the tire has some pretty good ratings. i wouldn't waste the money.
decent must have upgrades, no aftermarket out for the blazer yet, but you can buy the K&N air filter. bump up mpg a little.
accessories i am a fan of. premium rubber mats, cargo mat, window deflectors, molded hood deflector, molded splash guards, all relatively cheap, and i think they look great. good quality.