Re the missing episodes, although I haven't watched an episode of Hey Dude in an even longer time that alot of those other shows (because although I was a huge fan when it was originally on, I have a feeling it hasn't held up as well) I remembered reading somewhere about their being an episode that Nick no longer has the masters for.
Whatever the cause, the episode was considered “lost” in the fandom (although I was unaware of that). It was not (and still is not) available digitally on iTunes or Amazon Instant Video. It was, however, included on the season 3 DVD set and the Walmart-exclusive Complete Series DVD set.
However, the source used is a homemade VHS recording. I think. It’s possible that it’s actually a YouTube upload of a homemade VHS recording. If that’s the case, then there’s no telling what the video specs of the “source” that Shout! Factory used are. The resolution looks lower than normal (more pixelated). Motion looks a bit weird. However, the specs on the DVD are the same as for all of the other episodes. The episode looks…okay. There’s some tape damage. The very beginning of the episode (the fade-in) is missing, so it starts abruptly, and there’s the familiar “rainbow” effect that you see at the beginning of a homemade VHS recording. The fade-in to the second act is partially missing. Going by the running time, it seems around three seconds are missing. The audio seems to be in mono and isn’t as clear as that of the other episodes. Overall, though, it’s not too bad, and I’d rather have this than not have the episode at all. I just wish Shout! had put a notice on the box of the DVD set. I still would have bought it; I just wanted to know ahead of time.
It's an episode about Melody's brother having a drinking problem, so maybe at some point Nick got uncomfortable with re-airing it. I know that some of the banned Beavis and Butthead episodes are only known to exist in taped-off-TV VHS copies. If it's relevant, Nick and MTV were both owned by Viacomb.