Where can I get TM's Hydro pump and Rain dance?

There is no TM for hydro pump, but there is for rain dance. Rain dance is TM 18 and is found on the Abandoned Ship. No, you shouldn't replace sky uppsercut for overheat because overheat has pretty low accuracy and once it is used, your Special Attack gets desparatly lower.

A Pokemon that is level 100 can learn a move, but not by gaining levels. It can learn TM/HM's, it can be retaught a move, and can be tutored a move.

Those are the only ways of it learning moves. There is no specific TM store, but there is the Lilycove Dept. Store where you can buy TM's, and it is not definately (spelling???) not secret. Rate this answer.

Hydro pump isn't a tm.
No keep sky uppercut.
It can learn tms and hms but since it's level doesn't get higher then it can't learn any moves. No there isn't but there are places where you can buy and win some tms.

Keep Sky Uppercut. He can do all but level up any more, but Nutrients may increase his stats some(Protien, etc)but moves can be given/removed for sure.
You can get TM's all over:Lilycove Dept Store, Slateport Market, from various characters in the game(sometimes for nothing, sometimes when you do them a favor-talk to everyone!!), from the Gym Leaders after you beat them, inside those pokeball looking things on the ground, from a high level Pokemon in your party with Pickup ability(Zigzagoon/Linoone is one). Also, there are move tutors around the game who'll teach a Pokemon you pick his move(if he can learn it). And, in the Battle Frontier, you can buy moves with Battle Points you'll get from fighting(and winning, of course!).
No crazy questions...just crazy people! LOL
I gotta lot of good advice(as do many others on this board!!!)and if you'd like e-mail me at [email protected] about anything you feel too silly to ask or think is too detailed or confusing or whatever, write me and I'll respond as soon as I see it. (I love to encourage new Pokemon fans, so I extend you this as a Pokefriendly thing, I'm not a sicko!)
Enjoy! : )

Okay, here's the low down dude you should try blastoise and breed it with the Pokemon you have in mind ( if you told us why it might be easier to help) .

Which Pokemon you want to give it to or get it to learn) Second nonononononono never ever get rid of sky uppercut unless you have the PERFECT move to replace it get rid of something else if your not mentally retarded(figuratively speaking no offenses meant !)

Sky uppercut litterally saved my ass in the battle pyramid.
Yes of course 100's can I teach good moves all the time, and save hms for when I get weak Pokemon for my soul search.

This is a dream somewhat but wouldn't it be just dashing to be able to find them visit them and call them to see whats up( archie and maxie) that is.

Of course there isnt but it would be nice if there was. Contact if any more questions at [email protected], and i promise to go to the limits to help excluding downloading a entire cheat book