You'll want to check out the Swap n Shop thread (here's a link)
but you can access it from the forum home page for future reference
you can either start a thread to tell what you are looking for or peruse the sales and find someone selling a package. Just make sure the plants are right for your setup (low light or high light for example). In my experience (and I'm sure most people here will agree) you get a larger portion of healthier plants for a lot less money from the good folks here on TPT
Also, RAOK or ROAK stands for "Random Act Of Kindness" and you can usually get a bunch of plants for just the cost of shipping or less so look out for those too
By the way, welcome to TPT!!!
As for your other questions:
1) You actually don't need to let the tank establish again as long as you keep your beneficial bacteria alive. What has worked for me is putting all of the fish in a bucket with tank water and then putting the filter media and some of the plants in the tank with the fish. This way the beneficial bacteria are being fed so when you've got the tank reset up, you should only see a small cycle (if you see one at all). I used this method when I moved my 30 and 60g tanks twice in 6 months. Both times the fish had to hang out in buckets with filter media for a few days before we had a chance to get the tanks set back up but we didn't see any noticeable ammonia because we'd put the filter media in the buckets with the fish. Plants will house some of the bacteria as well so you could put some of the plants in the buckets along with the fish but you don't need to since the plants help by taking up the ammonia anyway
Also, the only thing you'll really need to remove the fish for is the substrate switch, after that, you can just plant away with the fish in the tank
It's a good idea to put an airstone (if you have one) in the bucket with the fish too, especially if you'll need to leave them in there for a few hours or overnight. At least, that's what we did and we didn't lose a single fish during either move
2) As a general rule, with planted tanks, you don't really want to "gravel vac" the way you would a non-planted tank (with the possible exception of areas that are intentionally left unplanted). That being said, pythons are very useful for speeding up water changes, and you can certainly run the hose near the surface of the substrate to pick up lose debris. If you do a search you can find a few threads on the topic. In fact, take a look at this thread
for various water change ideas (python is the probably the simplest because it's not a DIY it comes with all the pieces but it's a bit more $$)
3) There are various methods people use / suggest to remove excess snails from the tank. Keep in mind that having some snails in the tank is actually very good for it. In my experience, not overfeeding helps keep the snail population in check, but you still have some snails that help the overall health of the tank.
If it doesn't disturb you, you can smush the snails against the glass when you see them and your fish should take care of the rest
If not, there are various "snail trap" methods that people use with lettuce and other things, if you use the "search" function you should be able to get more info.
Good luck! And sorry about writing you a novel!