1. I mean, there are some techniques that you will be accustomed to doing that will carry over, such a Z-Canceling which is incredibly similar to Melee's L-Canceling, but as a player of both games, I strongly encourage you to look at them completely different. The more comparing you do the two games, the harder you're going to make it on yourself imo.
2. Watch videos, people like Boom and Stranded. Uair combos into itself a lot, and forward throw or up smash sets yourself up for uairs pretty easily. End with up b or dair if they're off stage and you have an extra jump to catch them with it. Falcon has a lot of moves that can work well with each other, but I think experience is the best way to determine how these moves flow into each other. Start simple, expand from there. (Edit: Upsmash pokes through Dreamland's side platforms, which can be very useful)
3. There's some decent resources here around the boards, but they aren't as active as they used to be. I find that you have to ask specific individuals for advice instead of finding resources, but that's just my personal experience on the matter. I say search the boards and if you can't find anything, ask it in the general questions thread or ask someone personally.
4. The community is quite sporadic, as there are people here on the boards, on the /r/smashbros and /r/ssb64 subreddits, on the multiple Facebook groups, on multiple Skype groups, the main IRC, etc. There isn't one solid hub that everyone has agreed on. In addition to that, there's somewhat of a split between online exclusive players and console exclusive players, with there being some people that juggle both. I wouldn't say the Melee community is necessarily laid back and friendly, but I won't say they're awful either. Each region has their own set of people, and it can vary from place to place. I've met some awful people in Melee and some awesome people as well. The same can be said about this game, but the important thing is to ignore any drama and just focus on the game.
Good luck and welcome to the community!