Not a big hassle. Very important to swap out the hammer for one with a fly, or install a fly in the current one. Also the sear if I remember correctly? The parts for a single set trigger can be had from MVA, and maybe elsewhere. (And if a hammer w/fly is sourced from MVA be advised you'll probably have to heat treat it. The last one I got from them got battered pretty quickly because I neglected to harden it.)

Simple solution would be to scout eBay and/or the classifieds here with a WTB ad for a complete lower tang with set trigger mechanism in place. Might take a while, might not, and probably cheaper than buying all new parts and assembling one yourself. Either way the hammer swap is important anyway.

I've done it on two now and it's not a daunting proposition.

To do a single set trigger properly you need a hammer with a fly, a sear with a notch so it does not wear off the fly tip, a trigger with a spring hole, a trigger catch and spring and a stiffer knockoff spring.  I have also had to install a weaker sear spring if the  knockoff won’t trip the hammer.  Sometimes a SST is a pain to get working properly but once done work well. 


MVA sells the parts but their hammer is the lower profile one as found in a low wall unless they have changed it since I bought one a while back 

While not as safe and against the better judgment of many, you could use a standard sear and hammer if you ground off the 1/2 cock notch.  I have one that was done that way.  As I don’t carry a rifle in the field I never use 1/2 cock anyway. 
Personally, I would look for a proper hammer.  They show up on eBay occasionally. 

Jack