Well, I just typed "Canada Gand Prix" into Yahoo and got the official site straight away. Prices are $415 for Gold, $340 for Silver and $185 for Bronze, all prices in Canadian dollars for three-day passes.
That's the information you can get off the web site. Now for the information you can get from someone who's already been there:
On the web site, the stands are numbered. Only the stands right in front of the pit complex are gold, so you won't really see anything special there. OK, so you'll see the pits and the start, but otherwise you're gonna sit there for 90 minutes watching the cars whizz past you. I would absolutely say that it's not worth the extra money.
The stands you want to go for are, in my order of recommendation, 11, 15, 12, 24, 21. 11 & 12 are down at the loop at the end of the start/finish straight. You have a giant screen so you can see the rest of the track, and there's a natural amphitheatre here, and it's a great atmosphere. It is about the furthest away from the public transport access points though (there is a metro runs out to the track).
15, 24 & 21 are down at the hairpin at the opposite end of the track. There's usually some overtaking here, and often some drivers outbraking themselves during qualifying, probably more likely given the new one-shot format. 15 is about 75m from the track though, so if you go for this stand, you'll need a long lens for decent photographs.
Don't forget that Montreal is in the French speaking part of Canada, so the commentary is often in French, and most people will want to speak French to you.
On getting to the circuit: Take the metro. It is not possible to park unless you're an invited guest, and the run out to the track is hugely congested, so a taxi will cost you heaps of money. On the flip side, there are regular metro services that will cost you about $5 return. There are lots of trains, so the conditions aren't too bad, apart from on race day, where there are huge crowds. You're advised to sit and sunbathe for at least an hour after the end of the race, to avoid standing in a fairly unpleasant crowd. It's about a 3/4 mile walk from the metro station to the hairpin end of the track. Add about another 1/2 to 3/4 miles to get down to stands 11 & 12.
The at-track facilities are pretty good, although there's not much in the way of stalls selling decent merchandise - pretty much Ferrari dominated.
And remember, always cheer for the BAR that isn't being driven with the guy with the Union Jack on his head!
Hope that helps...