Just bought a new guitar, Jackson DK2 with a locking trem. How hard is it to re-tune these things and what's required?
Your fingers. If it's major, unlock the nut and use the tuners. If minor, use the fine tuners on the bridge. Someone else can explain how to balance the trem, I cannae be arsed.
It's a pain to attempt to get the strings all in tune and the trem level, but after a few minutes (up to about an hour) of messing with it you should be able to get it. It's frustrating as all hell the first time you have to tune up.. and even the next few times as well. My suggestion: find a size of string that you like, get it all set up so the trem is level and stick with that size strings. If you change sstring sizes you'll have to either add springs in the back or detune your whole guitar.

A good method of tuning is tightening all the strings so there is no slack and they aren't flopping around. then starting with the low E tune each string up until they're in tune, it will take a few passes but it will eventually even out. A good idea is to overtune the low E and A etc. a bit so when you tune up the other strings the overtuning will drop to the correct pitch.

Good luck man.
Nor less I deem that there are Powers
Which of themselves our minds impress;
That we can feed this mind of ours
In a wise passiveness.

Sounds easy...

Could I just tune my guitar as normal up to E, as it's in Eb at the moment?
When i put strings on. I do it by taking all of them off, then putting all of the back on. I tune the guitar up as close as i can get it with the tremolo being parallel to the body(this is one way to tell how far you are in/out of tune) I dont lock the tuners, but i stretch out the strings a bit, and run through a few songs that require some bending. THEN i tune with the tuners finally, tighten the lockers, and then use the fine tuners to do the rest. Sometime i have to unlock it and use the tuners.
Ok, I just need to unlock the tuners, tune up and lock again?
Sure. Get as close as you can with the tuners at the top. And then once its tightened down use the fine tuners. Although when some people (like me) lock the mechanisms, it makes the open strings a little sharp because of the pressure. If you dont know what i mean dont worry about it. Just get as close as you can.