DirecTV question about upgrading receiver

Experts,

I am putting together my thoughts on making my own HTPC (or PVR) as a fun home project but I have come to a stumbling block. My TV service is currently provided by DirecTV and my current receivers are the Philips DSX 5500 which are not compatible with being controlled from another source other than the IR remote. I need to have a receiver from DirecTV that allows the computer to control it in order for this HTPC project to work well or even at all.

Just as an FYI on the background of what I am doing. I am piecing together a machine that will run Linux (Fedora Core) which will in turn run MythTV. From my research I have found a resource (http://www.pdp8.net/directv/directv.shtml) that will allow me to control my DirecTV box from the serial port with an appropriate adapter. But last night I took a closer look at my receiver and found that it is not on the list of supported boxes.

So, I just called DirecTV and asked what it would cost to upgrade (to the D11) and the thought of leasing it for $49 or buying it outright for $150 is not at all appealing. I tried to ask the person that if I could get another receiver (say off of eBay) would the service transfer easily ... or would they help if I had issues. The only thing that he would offer was the advice of, "We can guarantee that it will work if you get it from us ..."

This is my main question:

Has anybody done their own DirecTV receiver upgrade out there? And did it work? Easily?

I'm thinking of getting the D10-300 ... but whatever I can find out there good and compatible will be just fine. If anybody has any thoughts that they would like to share on my home project too they are more than welcome!!!

Thanks in advance,

Wally Atkins