geni install

The MPEG-2 shutdown is in-progress. It was supposed to already have been completed, but the pandemic and internal challenges slowed it down. Your D12s are on borrowed time. Either replace them or just accept to not have those 2 TVs when they stop working.

If I give up on the Genie idea and just service what is in place, what can I replace the D12's with, which I think are on RG59?

The MPEG swap, which would be a Genie and Mini Genie (Client, not receiver) would be free equipment and install. No new service agreement as well.

Alternatively, you can get HR24s through an authorized retailer (such as Solid Signal). But that would be at $199 (each) and come with a 24-month service agreement.

Personally, I would go with the MPEG swap as they do the work, the order is free, and no new service agreement. If you don't have the Whole Home DVR service ($3) already, that would be added to the monthly bill but then you can watch your recordings from any TV regardless on which box that recorded them. Unless paying $400+, and adding a new service agreement, is worth it for you to DIY.

I'm trying to avoid a service technician. What options are plug and play?

Plug and play on a legacy system is difficult. Unless those two rooms were already wired for DVR, then you cannot just plug in HR24s as each tuner requires a cable.

Closest you could get is HD non-DVR H24 (not H25 as that is SWM-only like the Genies). Would be $99 (each) for the one-time lease cost and still the 24-month agreement ordered through an authorized retailer.

You have to pay at least a couple hundred out of your pocket to avoid a tech.

As a note, non-Genie boxes are getting more difficult to come by as they haven't been made in years. DirecTV is just making boxes that are SWM-only which would be Genie setups.

All 4 rooms come through the SWM 16. 2 on RG6, 2 on RG59. 

If you have single wire going into all rooms (including HDDVRs), then you could do a couple more HR24s. But again, this will be out of pocket as DirecTV is not a business setup for DIY especially when dealing with legacy setups.