OK, if you've never worked on the trigger group of a 1911 before, you're not going to want to work on the functional safe factory trigger you've got now. IMO.
You can buy drop-in trigger kits, which have a sear, sear spring, disconnector, hammer, and mainspring all fit such that (hopefully) you have a safe, clean trigger of whatever weight you elect with no work on your part. At least that's the idea. :?
If you wanted to try doing some fitting yourself, but didn't want to risk ruining the factory trigger, you could buy a new sear like this one and see what you can do.
This page will give you a good idea what is entailed in a trigger job (he basically uses these stones with this jig), but even this guide shouldn't be used alone. For starters, he doesn't even mention the use of these sear engagement check pins, which are probably necessary for those of us who still need visual confirmation of our work.
Also good information to be gleaned over at THR and m1911.org.
The other thing to keep in mind is that the thumb safety is likely going to have to be adjusted (or even replaced) if you replace the sear and/or hammer.
On that note, if you ever do any modification whatsoever to your trigger group, always perform the thumb safety safety check described on the first page here very carefully before carrying the gun or using the thumb safety. Mere adjustment of the sear alone can change the sear/hammer engagement and thus sear/thumb safety interface enough that this check should be performed.
Barring any of that, get a gunsmith. :P