Shops typically charge $5 to remove a freewheel. That "silver thing" likely has a big round wire retainer spring clip around the inside circumference. If, so, a small bladed screwdriver is all that's needed, then it should just unscrew. You can hold the freewheel still with a rag while you do it.
There is a bike co-op in Sac that will help you out. Google "bike kitchen".
"Love is not the dying moan of a distant violin, itís the triumphant twang of a bedspring."
S. J. Perelman
Last edited by bigbossman; 12-12-08 at 10:06 AM.