The MkII trigger is very servicable if you know what you're doing and are careful. One of the tricks is to go slowly and take only a tiny bit off the trigger/sear engagement angle, as is depicted in the drawings and information you found on the net. A change of trigger weight spring is also in order. You can get spring stock from Brownells that is perfect for making your own trigger srping. It basically only needs to be cut to the correct length.
The steel of the receiver, where the trigger pivot is, is easy to drill. I drilled a couple of mine and threaded them with a 6X32 or 4X48 screw for an overtravel stop. I'm sure that Ruger would frown on this practice, but it's in a non-critical area and works just fine.
The main concern is the safety. Don't take enough off the trigger surface to affect the safety's ability to work properly.