The ABA26800AVP1 looks like it just the computering core (V2 means more ram, faster cpu ect.) I suspect the old V1 core runs software xxx30780xxx? and the new V2 core runs software xxx30782xxx?
That is how it works on the "Euro" version of the traction elevator and if the same goes for the Hydrofit, I would just replace the computering core with the new one and take the 8 pin eeprom from the old
board and fit onto the new board. Then you might get some "Bad Parameters" errors, you should be able to set them right, using the menu M-3-2 "Repair Params Menu".

But again, this from software xxx30782xxx (GECB Traction Euro) and may not be the same on the Hydrofit.

/Alex