Both Volquartsen and Power Custom make trigger/sear units that are very good and are pretty much drop in. Instructions are included. Check with Brownells (
www.brownells.com) for what they have and the price (not cheap).
Also, the original parts can be smoothed up a lot with a bit of careful stoning, but if you DIY, be careful not to change angles or you could empty a magazine very fast and get some unwanted attention at the range.
Jim