Newguy,
In my opinion(as a proud owner of one), isn't the Zeiss Conquest 3-9x40a bitlarge and heavy for the rifle you purchased? (I personally wouldn't even consider the Nikon)
Sounds like your definitely creating a half varmit/ half whitetail rig...the question is considering the money you are puting into will it really excel at either? (.243 not the best varmint caliber, the scopes aweful big and heavy for a lite whitetail rig...IMHO).
If I had to use the one gun you have already purchased I will tell you what I would do..
Purchase one pair of Talley scope bases and two pairs of Talley Screw Lock Quick Detachable rings. Sight the Leupold scope in for your whitetail load, and then sight the NIkon on in for your varmint load. Once this is done once you will not be wasting your time at the range multiple times a year sighting and resighting your gun every time you want to change between varmint and whitetail applications.
In the long run not only will it be cost effective by saving on ammunition costs, you will also have a few sets of great rings andtwo set ups. One that would be dedicated to varmints, the other to whitetails....both better thanthe original one scope choice...
Talley..
http://huntamerica.com/talley/#QD