Howdy,
Snake oil in a can is not the way to go. Even if it "works" for a while, you're just fucking the next guy. Don't do that. My guess is that it won't work for a while anyway.
The only way you can know if that's a reasonable # is to call around and get quotes. While I'm not familiar with this car, that's a job where a large component is going to be labor. You may well be able to find a non-dealer mechanic to do it for less, on the side, etc. Ask around your hockey team buddies for a local reference. It wouldn't surprise me at all if there was a lot of labor as the head needs to come off the motor and there's more and more shit in the way of that with modern cars. :-)
Depending on why its leaking, there may be other things that need to happen... if the head is warped, it'll need to be cut (machined to a flat surface) or replaced. If it can be cut, that's again mostly just labor but it may not be able to be. Same with the block. You'll know you're talking to a mechanic you want to do the work if they are able to speak to what the common problem is, whether its weak head gaskets, heads that warp, or whatever else
60k miles is pretty darned low for a leaking head gasket. Was the car overheated / run without coolant for some reason? Or do these have a reputation for this problem? I'm assuming there are some type of symptoms the car is exhibiting, vs. the dealer just telling you out of the blue that its got a leaking head gasket?
Mark
edit: There's no question that independents are out there that will charge you less than the dealer and who will do at least as good a job. Equally there are independents out there that will rob you blind and/or suck. The only reliable way I know of to sort them out is experience with them. With the dealer, one of the things you're paying extra for is someone to call if they fuck it up badly enough (in addition to typically more familiarity with the vehicle than a general all makes mechanic).