Building a lock from castings can look daunting. Just remember that there isn't anything that you can't do with a file, hacksaw and drill press. Other machine tools are nice too
There are a few hints that I'd like to pass along if I may.
First I hope you have a bead blast cabinet or access to one to remove the black crusty casting slag from those parts. It is abrasive and will dull your tools and files. If you don't have access to one then a cartrige case vibrater half full of kitty litter will work. Another advantage is that you can see your parts better and decide what needs to be done
before it becomes a problem.
I'd also suggest that you build it with the internal parts provided. That is a small lock and the parts are more likely to fit (that is a tiny tumbler) and the hammer timing is more likely to come out right on the first try. It looks like the screw holes are spotted for you and that is a big advantage. You will need to true up the tumbler axles and center them to each other - a lathe works but can be done on a drill press if that s all you have. Just remember to turn them to an existing drill/reamer diameter or you will be searching for an odd size reamer to make it fit the lock plate and bridle. Your lock appears to be unbridled. Ouch, they are a pain to drill the pivot screw hole and have the frizzen fit the pan when done. You will probably have to build yourself a jig from hardwood to hold the plate square with the drill press, drill through the plate from the back side and spot the frizzen then drill it free from there. Take your time, use sharp bits.
Making the springs springy and frizzen hard is another subject not to be included here. (I don't see a sear spring in the pile of parts) I build locks from castings every day, I'm willing to help or answer questions either on the forum or you are welcome to PM me.
Matt