Need help on A/C evaporator?

So I need to change my evaporator i went ahead and ordered one already its being ship as we speak. But i wanted to know how hard is it to change?
I rather the save the cash and do it myslef I know where its located and it only seams like theres a couple of bolts and screws holding it up to the firewall. I know I have to take the so call "black box" apart that house's the evaporator. The system is complety dry of r-12. So Im basicallyasking does anyone have any advice to give or some general tips on how to do it.

Also i purchased the r-134a conversion kit, i looked under the hood and I came to relize that I think i need to change the metal lines with the fittings on it. I believe there welded on, the kit jst comes with fittings has anybody ever done this before your input would be apperciated it thanks alot for your time richard

Those fittings just screw onto the old ones. Take a closer look. Also the evaporator is really simple to get in and out. Pull the glove box, there like 2 or 3 bolts holding it in. Undo the lines in the engine bay, make sure to unplug the thermostat on the side. And the drain tube. Also there are two screw-tightened bands on the inlet and outlet. After that it really just falls out. The box comes apart with like 12 someodd screws and is just two pieces of plastic with foam in it.

Thanks for the reply, one question about the coversion I forget to mention the year of the car. Its a 91 civic I'm thinking the 92 model is capable of changing the fittings by unscrewing them but I guess I can take another look at them but I swear they were welded thanks bro ....... Richard

Ill take a picture of my car, running on r134-a, with the fittings screwed on if that will convince you...