It's relatively simple.
After you have the slide off the frame, remove the safety. To do this, cock the hammer, turn the safety to the off position, and then push safety up just a little bit, and pull it out. Just a warning, the spring/plunger assembly will fly out, so be careful.
Next, decock the hammer, and remove the mainspring housing pin (I do this with a punch and a hammer). Be careful to not scratch the finish. After thats out, simply pull the mainspring housing out through the bottom (if you have an extended magwell, you may have to remove the grips by removing the 2 screws in each one first). At this point, the grip safety should drop right out.
Next, remove remove the sear spring by pulling it out.
Next, push out from the right side the pin that holds in the hammer, and remove the hammer.
After that, remove the pin that holds the sear/disconnector the same way you removed the hammer.
Next is interesting if you've never done it before. If your mag release has a flat head screw, use the sear spring or a small flatheaded screw driver. Push the mag release in as if to drop a magazine, and then rotate the screw counterclockwise. Once you get it, the mag release should drop right out. After that, the trigger will drop out.
If you havn't already, remove the grips and scrip screw bushings with a flat head screw driver.
http://www.m1911.org/stripin1.htm <--a good guide, with pictures.