Whirlpool Cabrio WTW6400SW2 tries to spin, but doesn't. Help!!

I have looked all over this forum and the web for a thread on this and can't find one so I'm starting this one.

I have a 2007 Whirlpool Cabrio WTW6400SW2 washer that cannot engage in the spin cycle. It sounds as though it is engaging, but doesn't have the power/torque to spin. It seems to start to turn, but then gets bogged down. Where do I start to diagnose this problem. Is it something I can repair/replace or should I call a repairman? Is it worth repairing?

Thanks,

Tom