upgrade and whole house DVR setup

I am replacing a defective HR20 that won't reboot. D* is sending a replacement by mail. I have OTA and the D* protection plan dept says I'll get the needed replacement equipment -- which should be an HR2x with an AM-21. I guess I'll believe it when I see it. I'm also planning to get whole house DVR set up by D* soon and the CSR said I should set up the new receiver myself and then call to schedule Whole house DVR. Before doing so, I want to make sure I end up with the best set up and the fewest "I wish I had known that before they came" moments. I could really use some help ensuring the set up I get makes sense and is future proofed at least a bit.

Here is my current set up:

1 HR20-100 (with OTA, separate OTA feed) being swapped out this week for a new HR2x?
1 HR 24
1 HR10-250 just connected to a SD TV
1 Hughes legacy to SD TV

The 4 year old 5 LNB dish runs to a zinwell WB68 (each receiver has two inputs so I'm using all 8 feeds from the zinwell). The OTA line runs from the roof to an Antronix 2-way splitter next to the zinwell. One feed of the splitter runs directly to the HR20, the other is diplexed to the HR10. I have not yet gotten an AM-21 for the HR24, but want to. I will need another OTA feed and the cable run, unless I should diplex it. I haven't set up the AM-21 before so am not sure what to expect there.

A few more details: The zinwell is outside 20 or so feet below the dish. It is adjacent to my basement wall, but I don't have a power outlet currently inside nearby. I also have AC ductwork just on the other side of the wall. Assuming I can get power to the basement location for the PI and close to the SWM, I will have issues with the current cable lengths and getting them to reach the power inverter in the basement.

I have a verizon fios actiontec 4-port router less than 10 ft from the location of the zinwell, though all the ports are now filled. If I need another port, that will take some doing as I will need a switch or second router, which I may do anyway to get gigabit ethernet. If I go that route, i need some time to sort out the router issues because of other equipment in the house that will work with certain routers. I currently have VOD wired thru a wireless sonos box near the HR20. It's the only box with VOD now and it works fine.

I've read some of the many threads on setup but am not wise enough to be sure what I need D* to do to properly set up the whole house DVR, feed the OTA to the 3rd box, etc.

Finally, I have always had D* future proof installs a bit. I convinced them to put in 5 LNB dish before I needed it. Got OTA installed even though we soon got HD locals. I got them to run dual cable where I had D* legacy receivers without DVRs. I will likely, but not for a bit, add another TV in the basement, and exchange our at least one more receiver for an HR2x.

Apologies for the basic questions here, but what should I be expecting and wanting D* to do here. If needed I can buy a new splitter for the OTA and run the cable, but I've often had success convincing techs to help me out when they are on site.

From my reading, it appears I will need them to replace the zinwell multi-switch to a SWM8. They could then use the extra coax runs for the DECA connection. Going this way, I then have the power access issues. Can I use an extension cord to power the PI to get it as close to the outdoor SWM as possible? Do I then also have legacy receiver issues for my hughes SD hdvr2?

The D* phone support person said I can use the HR10-250 for whole house DVR purposes. Is that right?

Thanks for any help.