Re: rem 700 sendero 300 win mag
My guess depending on condition (and it looks good) about $700.-$800. for the rifle, and about $300 - $400. for the scope. So about $1100-$1200 for the whole package if you sold it on the net. A buyer hot for this combo may well pay a bit more.
If you have the original box and papers for the rifle and scope, you could maybe squeeze out another $100 or so. I don't know why but having the original box and papers seem to add about 10% to the sale price.
Check out Gunbroker for used rifles and see what they go for. I think your best bet (in terms of $) is to sell the rifle and scope seperately. Ebay seems to yield the highest price for Leupold Hunting scopes. Gunbroker is a good place to list your rifle. I'm not sure how a hunting rifle would sell here in the classified section, but it's free and you might generate some buyers.
Good luck,
Bob