1). I'll do it for $49.95- including parts!
2). $85.00 sounds fair at the dealer, although its not that big of a job. You should have it cleaned, considering the mileage on your vehicle.
3). I've heard good things about BG 44K total deposit control fuel additive. Just dump it in the fuel tank before filling up. I am planning on trying it in the future on my Rodeo. $19.95 for an 11 ounce can. Available here:
http://www.ec-securehost.com/RynoPer..._Products.html
You may find it for less elsewhere.
Good luck,
Dale