Rear Wheel Bearing replacement jitters

My '99 Sienna has 230K and I'm going for 300K but, the rear wheel bearings are getting noisy and I need to replace both. The job looks easy enough but, I live in the Northeast and the thought of trying to remove rusty bolts that have been exposed to the weather for 12 years makes me a very uneasy. Snapping one of them would ruin my whole day. Has anyone who's actually tried had luck with it? Any other advice is appreciated too.:)