Agi
There are some videos out there as well as some other sites that will teach you how to do the trigger job on the 45ACP. I wouldn't hesitate to attempt it if you had the knowledge of how to do it and what you are looking for.
You will need to have the stones and a few other tools as well as a trigger pull gauge to use to check the pull with. I wouldn't recommend that you buy a stoning jig unless you plan to use it everyday, but they are available from MidwayUSA as well as Brownells.
Look at AGI for the videos, this is one I would recommend:
http://www.americangunsmith.com/view.php?id=21
they have several that deal with the 45ACP.
You might come over to :
http://www.homegunsmith.com/cgi-bin/ib3/ikonboard.cgi?
On this forum, you can read all about how to build up a 45 ACP into a very good carry gun. Frank Roderous has recorded most of the things that he did when he built a pair of Siestmas into a pair of very good shooting carry guns. It details a "how to" on the trigger job as well. If you go there, look at Roderous Custom Guns and then find the Siestema project.
Good luck with it. You could change out the parts and get a decent trigger pull if you get lucky. A lot of the parts are custom cut using CNC, but that doesn't equate to great trigger pull all the time. Some will give a crisp pull, but a crisp pull isn't all there is to a good pull. Most of the time, you will end up having to do some stoning. You can try to play with the spring, but like I said earlier, I only try to get the spring to reduce the pull by 8 ounces or so.