You don't need the Google toolbar! Firefox comes with the Google searchbar in the upper right corner, and it doesn't let popups through no matter what, so you don't need the popup blocker portion of the google toolbar.
And for the Ebay problem about going back to the top of the page, in situations like that, I will ALWAYS middle click on the link for the listing I want to browse. It will open in a new tab, then when I am done looking at it, I use my DOWN RIGHT mousegesture to close that tab, and BLAM I am right back at the big listing page.