Based on what your saying or what I gather, that you have a twin
dish 500 which is a dishpro dual Lnb setup. If this is correct, you will not be able to use the 2700 model receiver, since this is a legacy system. In order to use this receiver, you will need a DP adapter.
Also, you will need to insure that the 2700 has the up to date software, which I beleive is at 797?