b7, I don't blame you for wanting to upgrade. The heavier barrels do tend to allow you to shoot more accurately over a greater number of rounds. I suppose that you are also looking for some sort of an increase in accuracy, which you will probably get.
The downside to what you are doing is that the 700p barrel is still a stock factory Remington barrel. Bore quality aside, Remington barrels are notorious for having loose chambers and long throats. The long throat will have you loading your rounds really long to get close to the lands. The loose chamber may affect accuracy and will reduce the life of your brass. The combination of the long throat and loose chamber will also cause you to loose a good bit of velocity. From what I've seen, Remington barrels are also prone to copper fouling at the throat.
If you go over to site like Snipers hide, you'll see a lot of those guys loading their rounds out to overall lengths in excess of 2.81" just to get close to the lands and using rediculous powder charges to get the velocity that they want/need.
To gain the most benefit from what you are doing, my advise would be to first find a smith that really knows what he's doing. Not just a guy that can screw a barrel in. Have him take the barrel and knock a bit off of it at the breech end, then recut the chamber with a reamer appropriate for your preferred ammunition. This will get rid of the excessively long throat and with proper break in, do away with copper fouling issues at the throat. He can then headspace it to your action. Also be sure to have your lugs trued up.
Of course, the downside to this is cost and the reason that I don't mess with pull off barrels. After all is said and done, a couple hundred more could have gotten you a Rock, Bartlein or Krieger barrel. I am basing this on the assumption that you paid over $100 for the 700p pull off.
As far as the stock goes, shop around for a pull off stock, as has been mentioned. The HS Precision pull off are nice. If you shop around, you can find one for around $200, although I wouldn't pay more than that for a pull off. New ones run about $350. You could always check out the Bell and Carlson stocks. Their version of the M40 is pretty nice at around $200.
Good luck.