Romanian SARs and WASRs use a single hook trigger. All you need is the hammer, trigger and sear. They should come as a kit.
Have you tried firing it? It may not even have trigger slap.
As far as what to replace, you shouldn't need to replace anything. Try shooting it a while and see if it has any deficiencies that you think need attention.
I've tried a lot of crap on my SAR1 and except for threading the barrel for a flash suppressor, adding a Romanian side folding stock and an FSE trigger(to cure trigger slap), I've went back to stock on everything else. Nothing improved the original design. In fact, I've even considered going back to the original wooden buttstock, but I like how compact it is when folded.
Edit: Come to think of it, I did make one free improvement that made a big difference. I widened the gap slightly on the rear sight with my dremel (about two sight posts wide when sighting from the shoulder), rounded off the hard edge on the top, Gunkoted the entire rear sight flat black to reduce glare and painted the front sight post flat bright red to make it easy to see. IMO, that made a huge difference in shootability.