The Lyman pistol is an excellent pistol for a first time builder to start with.
It is basically, a factory pistol that has not had the finishing touches done but all of the difficult work (like drilling and threading holes) already exist.
These sometimes almost fall together but some require a small bit of trimming and minor woodwork to get everything installed correctly.
The more advanced kits like MBS, Pecatonica River etc. sell are little more than a roughed out wooden stock, a lock and a bunch of raw castings.
These advanced "kits" require some knowledge of doing accurate layouts, drilling and threading holes, filing and cutting metal and occasionally soldering.
These "advanced" kits are almost as much work as building a full advanced rifle.