Ok, so you are ordering 2 Keg Basic Keg Kit, Dispenses two kegs at once! (Separate Check Valves!)
I am pretty sure The upgrade removes the 2way manifold, and replaes it with the regulator. ($50ish for a regulator, $20ish for the manifold, $30 difference) and should not require any additional hoses/connectors to serve 2 kegs.
If you want to add a monifold after all that, then you would need additional hoses and DCs
I have not had my system long enough to have to replace any yet. I replaced all of my QD post orings, and dip tube orings when i got my kegs. Not all reconditioned kegs from vendors include replacing orings in the reconditioning process.
at my LHBS I can get post orings for $.15 and dip tube orings for $.10.