So is it possible to find the original lyrics of the instrumental "Let's Go Away for Awhlie", which was eventually unused in the final track?
Possible? Maybe. Probable? No.
As far as I know there's never been any indication of what any lyrics might have been. There are no unused vocals as such, no vocals were ever recorded, and whatever vocals might have been recorded, we don't know whether there were lyrics. Might have just been oohs and ahhs.