On the Senderos, they come with a H-S Precision stock with the full length aluminum bedding block (can't remember the model #). Like others have said, start with working up a load and see how it goes from there. I think someone already mentioned getting a new trigger, I would, the new Remington triggers are pretty rough. With that stock try to torque the action screws to 65 in lbs., it should tighten the groups up a bit. If you have the skills you can bed the recoil lug with Marine Tex.
If I had to make one recommendation to you, it is; if you want to change the stock and the barrel to lighten it up just buy a 700 SPS and save money for the changes to want to make. The barrel and the stock on the Sendero are pretty much the added cost on that gun. So spending the extra money from the start and then to turn around and spend more money to lighten it up, not really worth it once your done.