Yeah you'll need to cross over TxD and Rxd to use the sled, and also remember that the sled's serial provides 12V on pin 4, and also telephone mute and dimmer lines - none of which are present in the on-empeg serial port. You will need to lose these lines.

Since you (from your description anyway) appear to have a new reciever with a predefined serial connection, it sounds like your best option is to build a short cable to do this, using male connectors at both ends. (If you use a commercial available NULL modem adaptor then the 12V will still be crossed (to which pine

Cross pins 2 and 3
Wire pin 5 straight through. (Gnd)
Don't connect anything else.