Ouch. The thing is, there are desktop systems that typically run not too much higher than $600 USD (not counting monitor), although usually we see them starting more into the higher $700s, that can run the game not perfectly and without limits, but reasonably well. We can cut corners if all Game Options on high are not required and the heavier EPs are not to be in play, but I think this one just isn't in the right product class.
Would have no way of knowing if a processor can be upgraded on such a system, it really depends on how it was built and what it has for a system board. And I'm not enough of a hardware expert to answer that myself, so we would have to pass the info onto someone else. Graphics cards can be added to some systems, but I don't think that processor is going to work with one that is strong enough. And, in both cases, there must be an adequate power supply and a sufficient cooling system in place for the stronger components. Often enough what is possible will cost as much or more than a new computer to begin with. But it shouldn't hurt to ask what is possible and how much such upgrades might cost in parts and labor.
