What kind of seal and/or stain did you use on the wood?

It was sikkens, not sure which product was actually used but we specify "rubol" or "cetol" normally.

How high maintenance is this wood regarding up keep? Also cost compared to other types of wood like cedar?

Redwood is a little more than cedar, although both are kind of expensive. The upkeep is typically considered to be annual, unless you want the wood to turn gray, so that is a significant consideration when specifying any clear-sealed wood product.

where did you buy the wood, and how is it mounted to the house?

any lumber yard should be able to supply the wood. It's blind-nailed on the tongues.

sounds great. we are looking to doing something similar over rock that is lining one exterior wall of our home. I'm debating whether i build a frame over the rocks or attempt to remove them first.

OK -- good luck with the project!