First off, I'll say that Pecatonica River is one of the better places to do business with.
Dick Greensides, the owner, is a great guy and knows his trade.
That said, the Leman is perhaps the easiest of the "kits" sold by them, but this doesn't mean it is real easy.
Unlike the Kits sold by Traditions, Lyman and the other factories the kits sold by PR, TOTW, Chambers etc all require much more to put them together.
The payoff is that these gun "kits" can make very accurate recreations of some of the real guns that were made back "in the day" and they use some of the best American hardware available anywhere.
Where the Lyman, Traditions etc factory kits are their standard offerings in a unfinished condition requiring not much more than some sandpaper, finish oil and a screw driver the type of "kit" you asked about is not much more than a box of unfinished hardware.
The buttplate, trigger guard etc are rough sand castings that will require filing, sanding and polishing.
None of the holes that hold things together are drilled or threaded. The barrel will be a very tight fit in the barrel channel and the rear of the barrel channel will require the use of chisels to square it up and position the barrel.
The barrel usually is not breeched so you will have to install the breech plug. This requires some fine filing and a little profanity.
The butt plate is unfinished and the rear of the stock is not cut for it. It will require laying out the length of pull, sawing off some wood, reshaping the wood to match the butt plate, locating the screw holes and drilling them thru the metal and drilling the undersize holes for the screws into the wood.
The lock won't fit the mortice they cut and it will require some trimming and fitting with an exacto knife to get it installed.
The trigger slot isn't cut and the trigger plate isn't installed, nor is the trigger guard.
I could go on but this should give you an idea of what is envolved.
Note: For a small fee, Dick will install the breech plug, cut the barrels sight dovetails, cut the stock for the butt plate, install the barrel underlugs and a few other things for a very nominal price. Be sure to check it out, especially barrel breech and dovetails.
If your serious about building this gun you really need to buy a book that explains how to do it. Dick also will sell you a good book on the subject and I think he gives a discount if you buy the kit from him.
Also, visit the Gunbuilders Bench here on the forum. It will not only show you a lot of the things our members are working on, it is set up to answer any and all of your questions.
Now, after all of that, to answer your question in a simple way, a Factory kit like a Lyman or Traditions will take about 10--25 hours to put together and you will end up with a gun that is a little better than a factory gun.
A kit from PR, TOTW or the others will require at least 120 hours of work and often 160+ hours of your time. You will end up with an excellent rifle that is only available to people who can and will take the time to build it themselves or pay over $1000 to have a gunbuilder make it for you.