I'm going to guess, based on your question, that you have not engraved before. If that is not true, then you may disregard the rest of what I say!
I applaud your ambition to engrave the brass on your rifle. I have done the same, but am not a great engraver, so I am careful in what I do.
Engraving looks really nice on rifles, if it is done in the correct style and is moderately well done. Engraving in the wrong style, or that is badly done looks really terrible. With that in mind, make sure you practice enough before you engrave that 1000$ gun. If you are not satisfied, then leave it. The Kibler Colonial rifle is beautiful on it's own.
Many of the great long rifles of that period do not show particularly skillful engraving. But, and this is a big but, they show graceful artistry in the engraving. So even apprentice level engraving can pass, if the overall artistic design is good. If you haven't engraved before, then practice, but also look at the baroque and rococo forms that were used and make sure you can make graceful lines before you turn your nice Kibler gun into something less.
P.S. I'm not discouraging engraving, I'm simply encouraging waiting till you can do it at a passable level.
Cheers,
Norm