>Do I want to delete many URL's and have it be 404 error, I no longer sell those products, and they linked a lot of my pages one after another right in a row, and it has my domain name in bold. And how can I see what search engines have me linked now with my new URL's the easy way?
I would recommend using the .htaccess file to redirect them specifically to a "This product is no longer available page". If you have a seperate error page for each item, or group of items, it would give you more options to offer substitutions, and such. After all, isn't that what e-commerce is supposed to be about?
The other benefit of using the .htacess for redirect is some SEs penalize when you use header tags to redirect.