It's likely possible, but I'm not sure how likely you'd be to find the daughterboard. I'm pretty sure DISH used the same basic parts in all their receivers. The only difference would be what components are soldered into what holes.

It'd be easier to buy the parts and solder them in yourself. I know you said you don't have the guts to do it, but you might surprise yourself. Everything is well labeled, and the clearances aren't too tight. If you've ever done any soldering, then you can do it. I did mine, and I'm no expert or super-electronics hobbyist. Use a low-wattage soldering iron, be stingy with any extra solder you use, and verify your connections with a multitester. I upgraded my 3 year-old model 4000 without a problem (while watching the world series, no less!).

About the UHF remote...I've never heard of anything like a learning UHF remote. I imagine they don't make them because of the possibility of mis-use. Hang-out in a parking lot with your learning UHF remote, pick up a few signals from people arming their car alarms...you get the idea.

Good luck in your quest. I was about to buy a whole new receiver until I found the instructions on how to add the IR.