The Honda GCV (overhead cam) series of engines, including yours, are marketed as "Residential" engines, where the GXV (pushrod) engines are marketed as "Commercial". The difference is, essentially, how much they cost to build and how long they are expected to last. Hence the GCVs lack such sophisticated attributes as replaceable gaskets, an oil seal on the governor arm shaft where it goes through the side of the crankcase, a detachable cylinder head, and a gear-driven camshaft. This does not make them run badly, it just means they were designed with a lesser degree of attention to making them durable and repairable.
Remember, engines which have gaskets have places to put them. Engines which are intended to be sealed with goop only need places to put thin lines of goop. If you try for a gasket but do not design it correctly, you'll have an engine full of loose bits of gasket, which are pretty sure to be more of a problem than loose bits of dried RTV silicone.
By the way, it would be advisable to take a close look at the plastic cam that operates both valves. If the cam cover was really stopping the valves from opening, it has to have broken the cam belt, or wiped the lobe off the plastic cam, or flexed the pressed steel rocker arms to an alarming extent (those rocker arms have a reputation for breaking in service). It seems more likely the dent was on the other side of the rocker pivot, and it kept the valve from closing, rather than keeping it from opening. If that were the case, no damage is likely to have been done.
