You asked about a gasket and I failed to answer that. The basic answer is "it would be good to have one" but the truth is you can use RTV if you apply it correctly and go around all the bolt holes. I don't know where you live but those gaskets aren't really costly...I paid $4 the other day for one and have paid as little as $2. Alternatively you can lay the cover on top of a Pendaflex file, mark it and cut it carefully out of that. As long as you seal it well, you'll be ok.
