So I heard there are some mods to make the ValveKing sound even more awesome? XD

Could someone please give me some links to the tubes and speakers I need to get? Some place that ships in the USA xD Preferably Musiciansfriend.com.
Also a small guide to replace the tubes? Seeing as this is my first tube amp and I've never replaced them and would hate to mess them up. Thanks in advance.
Do a search on the forums. There are already a lot of threads about this.

The biggest upgrade in tone is a speaker swap. Many will recommend a Vintage 30. If it were me I'd get a Swamp Thang.

The second biggest upgrade is tubes. I leave it to the experts to offer you advice there.

The third is to add an overdrive pedal. Cheap solution, Bad Monkey, expensive but better solution, Tube Screamer.
I put a Vintage 30 in and love it.

To swap the tubes:
1. unscrew and remove the cage protecting the tubes
2. with a cloth(to prevent oils from getting on the tubes), pull the tubes straight down. You may need to wiggle it a little if it's too tight, but not too hard or you might snap the plastic thing on the tube (doesn't matter if you don't plan on ever using the old tube again)
3. match the pins (it only fits in one way), and stick the new tubes in
4.Enjoy new rich sound that will get better the more you play it

Black Schecter Omen 6
Mitchell MD-100S Acoustic
Peavey Valveking 112 with JJ's and V30
Roland Micro Cube
Visual Sounds Jekyll & Hyde
Danelectro Fish and Chips EQ
*Soon to Come*
Jackson USA SL2H
Peavey 6505+
Ignore the cloth & oils thing, that's utter crap.

Just pull the tubes out with your fingers, wang em back in. They'll need wiggling, if not then the socket is probably too loose. They only go in one way, it's hard to get wrong.
The Laney Thread are big and clever. No exceptions.
Preamp tubes I recommend 12ax7 Hi Gain Plus for hi gain or some 12au7's or some lower gain not sure about those if you don't want hi gain, and some hard to break up power tubes, matter of fact, how many power tube slots does the VK you have, have? If 2 match them with hard to break up power tubes, if 3 2 matched hard to break up and 1 unmatched easy to break up, and if 4 then 2 matched hard to break up and 2 matched easy to break up. The tone varies really, but that's my suggestions.

I have a Super Champ XD by Fender, and all I did was swap the stock 12ax7 for a 12ax7 HG+ by Ruby Tubes and it screams with so much more gain now.
I got some good guitars, yo.