97 grand am gt v6:

I've had a coolant leak for a while now and I think its leaking out of the seam from the resovouir tank. Are they pretty expensive? Easy to install? Dealership part?

They are kinda pricey from the stealership. Id check your local salvage yard. Or if you want a new one check the autopart stores, they should carry them, but might need to be ordered.
Easy to install just make sure all hoses are connected in thier original locations.