you can get it in google.com and type download google toolbaryou should get your download there
it depend son if your computers new if it is new it should pop up asking you if you want the Google toolbar
I haven't found one. There is an Answer by Answer.com extension which allows tho look up words straight from a text on another website.
Not if it's from Google, if it's from somewhere else, then possibly.
Google releases there toolbar for free. And it even is offered in most web browsers installation to install also. Answer. no