Defiantly go - it'll be worth it.
As Rainy and Goodvic said give the trainer a ring and explain things to her.
Classes are great, you'll find different dogs/owners are good at different things.
When I went there was a collie who jumped up and tried to play bite everyone but was so clever she was the best at all the commands. The trainer got everyone involved in calming her down.
Lilly was great at loose lead walking but wouldn't 'stay' as she would just follow me everywhere - LOL
The support form other owners was as valuable as the trainers it was great to be able to laugh at yourself when things didn't go well and celebrate your successes.