Personally, I wouldn't try it. Now, I don't know exactly which model of Gibson Explorer you've got (maybe post a pic or two or some specs?), but I'm assuming it doesn't already have a tremolo, correct? Most, if not all, Gibson Explorers have Tune-O-Matic bridges and stop tail pieces so, if you wanted to install a tremolo on one, not only would you have to rout for the tremolo on the top of the body, but also for the tremolo spring cavity in the back and that is a huge pain in the @$$. Additionally, because Explorers have Tune-O-Matic bridges, they also have an angled neck pocket to compensate for the height of the bridge so you don't end up with an action that's 3/4" high at the 12th or 17th fret. Tremolos (especially recessed tremolos) are intended for use on guitars with straight necks. On a bolt-on guitar, this wouldn't be that much of a problem. You can simply remove the neck, shim the neck pocket and then put the neck back on and have it be straight. However, you said you have a Gibson Explorer. As far as I know, all Gibson Explorers have set necks and set necks can't really be removed. I mean, it's technically possible, but I wouldn't want to try it.
is there any routing involved in installing a kahler tremolo?
Like I said above, unless your Explorer already has a tremolo, you'd have to rout for the tremolo spring cavity in the back of the body. Other than that, I don't know a whole lot about Kahler tremolos, so I couldn't tell you how much routing would be involved on the top of the body.
If you're getting a Warmoth Explorer, they can do that for you.
If it's a Gibson Explorer, no way... not unless you're Grover Jackson. Or Norm Abram. I agree with WMAG, sell it and buy a Warmoth. If you try it yourself you're VERY likely to f*ck it up and then you'll be trying to sell a trainwreck of a guitar on eBay. (We've seen some experiments gone wrong on eBay before.)
Come to think of it, I have a feeling that if you had the expertise to do it yourself, you wouldn't need to ask us!! :laughing7: