Matt, the right place to ask this question is actually the Symbian discussion boards. If you go there and look around (do all sorts of searches on MMS, receive, etc...) you may eventually find enough pieces of information to solve your problem.
But I must say, that it really will be *pieces* of information. Search our website for everything else you can find that is Symbian+MMS related. I *think* there are just a couple of sample applications there, and I presume you have already had a look at both of them. Our MMS offerings on the Symbian side are just not sufficient, imho.
Myself I'm only just learning Symbian, but my intention is to try those sample apps myself as soon as possible, and as soon as I can, try to fill in the huge gap that is our Symbian MMS documentation. In the meantime, all sample code and or tips that our developer community feels like sharing are MORE than welcome.