I'm looking to get a 5W Blackheart-112, running an epi standard or custom through it with a bad monkey od.
Lots of people recommend replacing the tubes, but I have absolutely no experience with types of tubes or what exactly each type does. I'm looking for a good zeppelin-esque tone, hopefully while being able to play some decent Eagles and Clapton.

Can anyone recommend some good tube brands/types and let me know if replacing the tubes is as simple as unscrewing the amp, unscrewing the tubes and replacing them? And if replacing the tubes is worth the money
try out the stock tubes, you never know.

im no expert on tube sets, but i do know that they just pull (gently) out of their holders, then push the new ones in
Get off this damn forum and play your damn guitar.
search the threads, there is plenty of info on tubes
Suhr Custom, Flaxwood Rautia or Grosh Tele thru
HBE Medicine Bawl Wah
Analogman BiComp
Texas Two Step OD
Fulltone Ultimate Octave/Fuzz
Boss CE-2
TC Nova Delay
SLO-100, 65 London or Bogner Shiva
Ask me about any of this stuff!
You have one 12AX7 and one EL84 in that amp. You might want to wait before you get it and then post in the tube thread how you want to tweak the tone, but a good starting point is a tung-sol 12AX7 and a JJ EL84.
With that amp, replacing tubes only requires taking the back off and pulling the old ones out. DO NOT try to unscrew them; they're not lightbulbs. They have pins on the bottom, just pull them straight up and out of the socket.