You have plenty of gun to shoot 1000 yds, rest assured. The 7mm is my personal favorite LR bullet and the Weatherby sends them downrange in a hurry. I shoot a "pretty much stock" 7mm Sendero. I have great glass mounted and have worked up some great loads and I seem to do as well as my buddies who have 4 times the money invested in their rigs than I do. Your .243 is no slouch either for that matter. I am going to approach the question from the perspective that you have already a decent knowledge base, but I think it is wise to take a practical approach. Start out shooting a lot and up grade as you go.
First the idea is to have fun and to learn (in that order). The learning curve isn't all that steep, or it is tremendous. Both a true statements. There is a huge knowledge base on this site and sometimes you cannot say much without saying almost everything. Avoid the confusion and have fun at the same time. Shoot the gun! Shoot when it is windy, wet, calm, hot and cold. Each will teach you something different. A big factor in what to start out with is what you want to use the rifle for. My LR guns: 30-06, 7mm RM both have to pull double duty as hunters and LR guns. They have been plenty good at both assignments. My Ruger #1A in 45-70 gets wrung out now and then as well as a "relatively speaking" LR gun.
In my opinion the worst thing you can do is invests heavily in "stuff" that you see other people using or that they recommend. Instead, shoot that rifle as much as you can, then add things, starting with a quality scope, as you master the unique specifics of your rifle at ever increasing ranges. A 3x5 index card with drop data is more meaningful in the beginning than most people give credit to. One "must" is to bed the action and float the barrel. Second, a good chronograph will, at some point, be needed to develop and tune the perfect load for your rifle.
In short you are good to go, but there are always some tradeoffs.
Your stick may have a few drawback: it is probably a thinner barrel hunting rifle, so you should observe a barrel cool down of 5 minutes between rounds fired. (shoot your 243 while the beast cools down-you may be surprised to learn you have 2 LR rifles because you simply shoot it better, especially in the beginning. Unless the 7 has a muzzle brake, its recoil will earn your respect after only a few rounds. Practice from the prone properly, each and every time until it is automatic. And start out at more modest ranges until the basics of your 7 are second nature.
The Weatherby is greatly over bored and it therefore much tougher on barrels than say the standard 308. Also, it is a powder hog, more expensive to reload than non-Weatherby cartridges and seems to have fewer after-market stocks available for upgrades. The factory stock isn't the best for long range shooting but it will be more than adequate for now.
Put some trigger time in and move to longer ranges as you learn the fundamentals: range estimation, wind , proper shooting position, cheek weld, breath and trigger pull. the more time spent shooting means more time learning to make your rifle an extension of you arm eyes, fingers and shoulder.
Then after a long time doing this you will discover that "the perfect" long range rifle is the one you can hunt with, ring steel and punch paper with.
Good luck
