FB marketing - FB Fan page, worth it? What about complaints

Hey guys, first post here, but I'm a long time lurker.

I own a website, last year we did roughly 1.5m in sales, the year before that, 650k, and this year (with the economy kinda funky) only around 800k. Still things are well, but we don't like slow, and we hate that it's "slower" than last year. We sell only one product, a car part. Our website boasts about how we offer installation support, great customer service, etc. Our product saves MPG - so our customers are eager to purchase.

Recently sales have been declining, we're seeing more of our/potential customers using social networks and mobile devices to shop - so it's time to get optimized.

My question is, does anybody have any experience with owning/managing a FB/Twitter fan page when a physical product, that almost always require a "follow-up" or "service request by the customer"? Around 99% of the time, our product requires the customer to either call us, or open a support ticket. This is because we offer installation support, which is rare, so they're not too upset. My concern is, with this service being offered to our customers, I'm worried that our Facebook page will be flooded with "how do I install it" or "how does it connect to my car", etc etc. If that's the case, I don't really see much value, but then again, I don't have any experience. I also don't know how valuable it really is to sell products via Facebook - is it really that good?

So far we've done SEO - just started again, been burnt in the passed. And adwords. 99% of our clicks are from adwords, and we're spending roughly $30k a month on it, so we're definitely looking for ways to increase sales without increasing our budget.

Thanks for the any and all advice in advance!