I would stay away from a TRS 'kit' at this point.
They take a lot of work, not the usual clean up of the metal and wood inletting and presto,,there's your rifle!
Their stocks are nortorious for sloppy inletting of the hardware pieces and I can attest to that.
You will spend a lot of time fixing oversize (pre)inlet areas to make rough cast metal parts fit.
It is certainly good practice for restoration work if that is what you are looking for.
If you do go this route, the excellent advise to have them inlet the bbl only and rough turn the outside stock contour ONLY is a good one.
Maybe do the ramrod hole too. But so you know, They often do the RR hole in the lower forend my milling down inside the the bbl inlet. Not the full length drill-it-out operation from the muzzle.
Metal parts are 'as-cast' and are rough. They take a lot of filing up to get them ready to inlet.
If the part is undersize to the pre-cut stock inlet, you are really starting from behind the 8-ball.
The side plate on a Queen Anne Musket was so bad I just ended making one from scratch.
Sometimes peening the metal can stretch it to meet the oversize inlets,,sometimes not.
The bbl inlet was very nice though.
It did take some spotting and scrapping to get it down in position, but about what I expected.
Here's a couple pics of what the parts look like as recv'd and one of the springs (frizzen) all polished up ready to be hardened.
The sear spring provided was un-usable so I made a new one from scratch.
Lot's of work as I said.
Trimming up a repro Charley would probably be the best bet. Everything works and is inletted already. You can
refit things you want and can do. Spif it up, reshape wood, refinish metal, work over the lock for better performance & smoother operation,,etc.
But you have an assembled musket in hand to start with.
It's a better first step IMO to build new skills and confidence. Then you can go one to one of the kits like a TRS if you feel the need and really like to file & polish stuff.