I have a 60's Tribute Studio Gibson Les Paul with P-90s. Lately, I have been thinking about customization with this guitar (I have 5 others) so I read up on the Gibson website about different types of pickups they have. Since I'm a 16 year old girl, I figured I'd ask the world of guitarists if this is a dumb idea or not before I embarrass myself in front of the guys at my favorite guitar shops. I also have the worry of really messing up the guitars if I do something stupid; so I stick with little things for now like adding springs to the Strat. xD

I came to the conclusion that I might like p-94s in the Les Paul: You still get to keep a p-90s sound with a little more crunch like a Humbucker, if I'm not mistaken. I would go for a straight Humbucker, I love them covered, but the body is chambered so I feel that that wouldn't be such a great idea. (I really should have waited and bought the used standard I found like a few weeks later that was all solid and had humbuckers with the honeyburst glossy finish, but oh well.)

So, when it comes to switching out pickups, I've read a few things but I still have a few doubts. Including as to whether if you need to make the pickup slots bigger (which means cutting the wood ohgod.__. ) depending on which pickup you choose to put in, or if they all tend to be the same general size.

I love the guitar, it's my first Les Paul and I'd like it a bit crunchier, though I love p90s (I have a '65 reissue elitist casino, perfect to satisfy my love for p90s)

All in all, I guess I'd just like opinion and some information on my "case". xD
I even get scared if I might accidentally screw in the strap locks too far and crack the wood on all of my babes. xD
Ok! There's a lot to go over here.

1. The P-94 isn't in between a P-90 and a humbucker tonally. It's just a P-90 in a humbucker size housing. Seymour Duncan makes a pickup called the Fat Cat that's the same thing. I think Rio Grande and Lollar also make something like that. It's a fairly common product. These pickups aren't practical for your guitar, but I'll come back to that later.

2. There's no solid relation between a chambered body and a humbucker, covered or uncovered. I'm confused as to why you made this connection. The weight-relief chambering used on your Les Paul is designed to keep it sounding like a solid guitar. It won't turn it into a semi-hollowbody; the difference is small (but significant) and it doesn't dictate what type of pickup you choose.

3. Your guitar has a route for a P-90 sized pickup. That's smaller than a humbucker route, so you cannot use a humbucker sized pickup. You could route out a bigger pickup cavity, but that would be impractical given that you could instead just trade your P-90 guitar for a very similar one with the right route.

So you can't use a humbucker-sized P-90 like the P-94. What you need is actually the opposite, which is a P-90 sized humbucker. That's a much less common product. DiMarzio makes a pickup called the Tone Zone P90, and the Duncan custom shop will make you any pickup you want in a P-90 housing, and I'm sure some of the smaller custom winders would too. But your options if you want a humbucker are fairly limited.

My suggestion would be to go play a bunch of Les Pauls to make sure that you really want a humbucker sound. It's probably most practical to either get a different set of P-90s (hotter ones than Gibson uses would give you more crunch) or trade for a humbucker model. Installing humbucker type pickups in your guitar is a bit backwards.

If you're somewhere reasonably well populated, you could probably find someone on your local Craigslist/Kijiji/Gumtree/whatever who would want to trade a humbucker Les Paul for your P-90 one.