CMWill:
Your enthusiasm is certainly refreshing, but don't discount other posters as 'knockers': they are simply speaking from experience which you are only beginning to accumulate. However, you have come to the right place!

I could be a bit of a 'knocker' myself, particularly regarding your proposed cosmetic work on the Spartan (you can't make a silk purse out of a sow's ear!), but I think you simply need to read a lot more round the topic, and keep asking questions here. You could profitably spend a lazy Sunday afternoon going back a year or so in this very forum, reading all posts relating to shooting or loading for double rifles.

Regarding books, follow Ron Vella's recommendation for info on rifle-building. The best book on reloading for doubles is Graeme Wright's "Shooting the British Double Rifle", which will set you straight on a lot of issues, including why you can't laser-sight the barrels to regulate a double! Buy a copy!

Hope this helps.