I'm getting into slide guitar recently, and I want to raise the action of my LP a little (I've been told this is the best bet for playing slide), but I'm not entirely sure how, and getting it setup professionally is not exactly cost-effective, so I was wondering if anyone had some tips or links on the best way to do this, and then how to change it back afterwards.

Les Pauls will have a Tune-O-Matic bridge, so i would slacken all the strings... then use a screwdriver on the screws on the bridge to raise the action. Make sure to do it evenly on each side. Its pretty simple to get it back
it has a really good distortion and clean sound a little to much hum in the background but i guess thats why they call them humbuckers"

review on Zzounds
but that would affect intonation or not?

Guitar : Fender CIJ Mustang and a Telecaster
Amp : 76 fender champ
Pedals : BBE green screamer, Big muff, Ibanez LU20 Pedal Tuner, boss loop pedal
How do I make sure everything's level once I play around with it? It seems like there's a large margin for error, and I'd rather not screw up.
There's no margin for error,it's all totally reversible.just don't screw with the truss rod.

All you do is raise the bridge and the saddle and then fix the intonation.
It's stupidly easy to raise and lower the action on a Les Paul.

If you're worried about the height being uneven, use a caliper/ruler/gauge wire.

As far as intonation, generally you configure that by fretting the 12th fret, making sure the string is in proper tune. Adjust the saddles such that at the 12th fret, you are exactly one octave higher than when you play an open string (i.e. 12th fret E string should be an e, not an e# or eb). It's really not hard.

There's no way you can break your guitar while raising and lowering the bridge. Just be sure to loosen your strings a little so you don't snap them.