You cannot change what in the PC world is memory. Newer has more.
Again, my sincere appreciation goes out to all those who have chimed in.
I heeded your collective advice and got the newer version, 12.9" Pro with 64GB of
storage. It arrived today and appears brand, spanking new. Also nice to know that Industrial Designers find gainful employment at Apple (every detail, down to cable wrap and box seal, is a work of art). Just topping off the battery and updating firmware now.
Still a reluctant "convert", but refurbished direct from Apple was definitely the way to go!
Dave