Well the 7D is about 17 hundred brand new and 5Ds are going for about 9 hundred or so, so figure your gonna have to make it worth the persons while. Not to mention that people that own 7Ds really like them so your prolly gonna have a hard time convincing people to trade in the first place. You might have an easier time selling you 5D to someone looking for one and also selling the other gear you mentioned and just buying the 7D brand new
I might be wrong wrong on the selling price of the 5D by a couple hundred or so
7D is 1700 with a lens ( $1400 ish without one ), Brand new. Im looking for a used one - without lens. Also something to consider. 5D on a good deal is $900 average deal 1000-1100. So i would say id throw in $200.