The transmitters and receivers that were designed and built in the '70s required lots of discrete components. The up-converters, amplifiers and matching networks will still need to be discrete components, but I'm estimating that the other 80% of the radio equipment can be implemented as a software-defined-radio (SDR - see http://spectrum.ieee.org/geek-life/hands-on/a-40-softwaredef... for an example).

I'll be reaching out to a friend and former colleague who specializes in this type of hardware/software.

I have no expectation that we can replicate even a tiny portion of the DSN, but I'm talking with people that already have big dishes and tracking capabilities. Remember that we don't have to talk to this spacecraft continuously. I think even downloading the last of its collected data would be a win but positioning it to do more science, then collecting data from it again in several months/years would be really cool.