Changing just a heater box should be a pretty simple self project. That's basically what I did. Installed the d4 leaving all the plumbing and thermostat from my d2. It was pretty simple swap.
First you need to go to a cat scale with you, fuel and personal items aboard. Then you will know the true weight of the van. You might be suprised but your already probably using several hundred lbs of that 2000 allotted.
And call them. You might also come up to the expedite expo in Wilmington oh next Friday and saturday the 24th and 25th. You can get face time with recruiters plus talk to expediters, we are an aproachable bunch.