Whatever you do, do not varnish over the existing coating. It will, in time, laminate and then start peeling out. That said, remove the coating you have by either sanding or using something like Formby's (hard on urethane. Sand lightly after that, and then start with a satin urethane or a product called DEFT. Use steel wool between each of the four coats you then use a tack cloth between each coat. Then, on the final light coat,do not use the steel wool. Be sure that the coats are 48 hours old before recoating.
If you put anything in the bed that could scratch it, use a moving pad under it to protect your investment.
