How much to replace the valve seals on the engine?

Check locally for pricing may be pcv system clogged or a head gasket maybe. Have a pro give you a diagnostic and price

I have seen the drain back holes in the right side cylinder head get clogged up with gunk and fill up with oil. This is probably your problem, I would remove the valve cover for inspection first. Here is how. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.