Good deal on the liner. That's the hard part so it will stay intact for years to come. As for the sealant the same type you would use toward something such as a patio decking would be good. The only areas I would keep an eye out for are close to the soil line of the outer wood. Sorry but I've been outta the game for a bit and can't help you there.
RE: Berry Bliss. My first Raised Garden!