If the head gasket went south you should check the head and block for warping and have the head magnafluxed to check for cracks. Most likely the head will warp and have to be surfaced. Not expensive but necessary to do a proper job. I would check if Felpro makes a head gasket for your application. Their gaskets are top notch.
As far as sealants, they are a poor substitute for proper mechanical work. However, a can of regular ground black pepper, 4 ounces or so, dumped in the cooling system will cure most any leak or crack.