Welcome to the campfire!
I looked in a gun book at a store last month and it had the gun listed as being worth "new in the box" at $6000.00, used in good shape at $2500.00 and the low price was $1400.00..
However mine is not for sale at any price, I bought it to hunt with, I do other things to make money.........
Sounds like you have a winner, though I have to admit to cringing any time I hear trigger work being done on 99's. As to the values listed in the book... WAY off. Watch gunbroker, you can pick up NIB ones for under $1000 consistently if you want to. You are the exception By hunting yours, most folks bought them as collector pieces and there are thousands still out there that are NIB. A NIB 99C from the same year would probably sell for more.
A $6000 99 is likely to be a very nice engraved old 1899, not anything made in the last 70 years.