As you've found, there is a lot to putting one of the "kits" from places like Track of the Wolf, Pecatonica River, Chambers, etc. together.
I've built over 12 of these guns and can say that even the simple, bare bones versions can easily take over 100 hours to do it right.
(I spent over 180 hours on my first one and I've never spent less than 140 hours on one.)
I mention this because paying someone to build your rifle can easily cost over $800 and that's only if the builder is willing to work for less than McDonalds pays their burger flippers.
IMO, your other option is to ask for help from us here on the forum.
We can usually help people with almost any problem they have, possibly even being able to help you with your guns tang problem.
The important thing to remember is, building your gun is going to take some time and, ask your questions before you actually do something.
It's a lot easier to find out how to do something before doing it that it is asking about how to fix something that was messed up.
Hope to hear more from you about your tang problem.