"...what is going to keep those with higher expertise and knowlege from dominating the decision process and in the end becoming a an elite group or class with more privileges and power?"
I know nothing about parecon, but aside from parecon, the answer to the question is
1) democracy 2) a culture that does not worship individual "success"
As Emily put it,
I'm Nobody! Who are you? Are you - Nobody - Too? Then there's a pair of us! Don't tell! they'd advertise - you know!
How dreary - to be - Somebody! How public - like a Frog - To tell one's name - the livelong June- To an admiring Bog!
Joanna