OK, there's some important things that will make this easier:
1) Pull the grip panels.
2) Cock the gun.
3) Put a cross-pin of some sort made of decent quality metal (not a paperclip!) sideways through the bottom of the mainspring strut (part 29 on that diagram).
Now when you lower the hammer, the mainspring, mainspring strut and the "keeper" will all come out in one piece. Leave 'em that way if possible, otherwise you'll have to reassemble that group back to that point to get the gun back together.
The other tricky point is the "three hands problem" when depressing the one "flat spring" in the whole gun, and it's...WAITASEC, that's the WRONG PICTURE FOR YOUR GUN!
45LC Blackhawks were built on the New Model frame. That's an old model. Different innards!!!
You want:
http://www.brownells.com/aspx/NS/sc...721&m=13&mn=Ruger®&model=New+Model+Blackhawk+
Now as I was saying: the spring at part 17 is a pain. Once the grip frame is off, flip the gun over. Pushing inwards on that spring allows a cross-pin to slide out, it's the pin the trigger pivots on.
What else...on disassembly, watch out for the spring at part 37/38. It may come popping out of there. And on re-assembly, the spring-loaded plunger at part 6 and 7 can break if you're not careful.
When putting it back together, it's easiest to leave the legs off of the trigger return spring. The end touching the trigger will fit in easily and then once it's all bolted up put them back. Also, when putting the grip frame back on be sure not to "guillotine" the end of the spring at 37/38.
Don't let these issues worry you too much, as all of these parts are cheap replacements
.