There are others that will have much better information than I will and much more experience in this area but I will put my 2cents out there anyway.
There would be a few questions that would make the answer a little easier and I would think you would want to answer before proceeding, like: What is your current deer density? What is your carrying capacity on the 1800 acres? What is your current buck/doe ratio? What is your current age structure? Etc...
Without that information, I would assume that you have the answers to those questions and have an idea of how many deer per acre you can reasonably carry and physically keep on a LF place. I would also assume that you would have an idea of the deer that you would want to "replace" in the native herd that currently resides on the ranch.
Since you are talking about purchasing 10 bred does, it would appear that you are working on a long term plan in an attempt to increase the maximum genetic potential on your place over the course of multiple generations and aren't looking for any immediate impact. IMO, to attempt to increase the maximum genetic potential, you would already be at the maximum genetic potential of the native herd and are currently maintaining that.
Once you release the deer with superior genetics, what is your plan to keep them from getting shot during population control measures and maintaining your CC?
I have watched a HF ranch that only had native genetics within the fence do basically the same thing. They did not work through many of the issues I have mentioned above and their herd was not at the maximum genetic potential when they started releasing the bred doe and when they introduced high end bred bucks into the place. The native genetics washed out the superior genetics and the top end was not increased due to the introduction. On occasion, some odd ball deer would pop out that was well above the average, but not worth the $40k they spent in introduction of the superior genetic animals.
I haven't priced bred doe and the price will depend on the caliber of buck that they were exposed to, but I would assume you would pay around $2000-$2500 each.
Even if I had the money, I wouldn't do it, but if you and the owner decide to do it, I hope it works out for you! Good luck