First off what do you want to do with the rifle that you want to change the stock and barrel? What kind of groupings are you getting with this rifle? If it isn't shooting for you anymore I'd try several things before I replace the stock and barrel.
I've found most Weatherby Vanguards to give very good accuracy for hunting. I don't expect bench rest accuracy out of my hunting rifles but with the right ammunition most of mine will do 1.5" or better with 3-5 rounds. I hand load to find the ammunition that works best in my rifles, but you should be able to find a good factory load if you don't roll your own.
If it is loss of accuracy check the scope and mounts and they could be loose. Use a good copper solvent to clean the barrel to remove any chance of a fouled bore. Might even take the rifle to a gunsmith and have a bore scope ran down it to find out the condition of the barrel. Don't forget to check the crown.
What is the trigger pull like? A good trigger job can greatly increase the accuracy of a rifle. You might need to bed the action as well to get a better fit to the factory stock. Bedding an action regardless if you free float the barrel or full length bed usually increases accuracy.
All of this stuff if you pay a gunsmith to do is still cheaper than replacing a barrel or stock in most cases. Now if you want to try a different caliber remember you will have to stick with a case that has the same basic dimensions as the 7mm Rem Mag, if you don't want to modify the bolt and feed rails. So calibers like .300 and .338 Win mag, .375 Ruger will work for a caliber change as well as several others, but using a case with a different rim diameter will make a caliber change a real PITA. If you want to stay with the 7mm Rem Mag I wouldn't change out the barrel unless that is what it takes to get acceptable accuracy for hunting out of that rifle.
Now if you just don't like the stock and want something different that is ok too. What do you like better Wood or Synthetic stocks? In wood you can get from plain walnut to some really fancy wood with a lot of character. Pre-inleted wood stocks usually take some final fitting to get your action and barrel to fit as well. They require finishing as well with a good linseed oil and lots of elbow grease.
Synthetics are usually easier to just swap out but don't look as nice IMO, but are more durable and you don't feel as bad when they take a beating in the field. Laminates are a compromise between wood and synthetic. They have the feel of wood and come in a variety of colors and are close to the durability of a synthetic stock.
