I installed my A/C in my 95 wrangler last summer. It was a straight foward easier than it looks install. I bought a complete kit. you will have to drill 2 holes in the firewall under the glove box, not a big deal just use a hole saw bit. everything already has a place to be bolted onto, which is nice. one thing you should do, which i didn't, is connect the hoses to the Condensor before bolted it in front of the radiator. you wont have to drain and remove the radiator if you have a 2.5L engine.
as far as how it runs with the A/C on... it does accelerate a little slower but you can't really tell that much. i mean it is a jeep so its not like your speeding around anyway.
you should be able to do it in a weekend.