Where and how do you think is the best place to "place" google adwords on OScommerce template. I have a basic template right now. Also Do you think it would actually work or do you think that adwords on a car parts page would turn people off and make them leave because of adds every where?
I don't think the ads will really turn people off, just bare 2 things in mind. Don't let your adverts distract from your main product. Don't make getting a high CTR your main objective (this often ends with the website putting adverts in really annoying places, like right next to a piece of text a picture or menu with no border) Some suggestions are near the footer of your pages, perhaps on the "thank you" page when someone completes an order.
Ads definitely do not belong on as commerce site. I really don't under why people do this. a. It screams amateur. b. Why would you want to send potential customers elsewhere? Basic brick and mortar principles apply online too. Would you walk up to a customer in your store and send them elsewhere?
I think that you meant AdSense (not AdWords) anyway. Always remeber the rule. Focus your page on one action or event that you want the user to take when they visit the site. Wether it is a registration, purchase or anything else. Make sure that all copy, graphics, everything drives the user to that action. If you can earn more using AdSense then you can from your product, then focus your users toward the AdSense ads. If not, then stay away from outside advertising (like others suggested), and focus your users attention on buying your product.