It is not using a desktop processor its using an intel B series chip which is a mobile chip like all past Mini's. I don't know of any Mac mini that has has the CPU upgradable post purchase and yes its soldered in place.
It is at least possible. I bought a first gen intel single core mini off ebay and installed a dual core MB processor into the same socket. But it may not be still possible.It is not using a desktop processor its using an intel B series chip which is a mobile chip like all past Mini's. I don't know of any Mac mini that has has the CPU upgradable post purchase and yes its soldered in place.