Thanks Neil and Babowa.
Yes, the memory specifications do say "user accessible". The disk drive is also accessible, but you have to take it apart to get to where the drive is. Several videos on iTube showing how to do this. Looks like it is not an easy job.
I'm wondering if it is worth the extra $200 to get the Retina display. You also get a better video card. I've heard that for normal computing the resolution of the Retina display so high that when using the maximum resolution the text is so small that it is hard to see and so you set it for a lower resolution. I don't do movie editing or extensive photo editing. Probably won't watch many movies on it, although that would be a temptation with that 5K resolution.
I am thinking seriously of getting the upgrade to the 1 TB Fusion drive (also get a 3.5 GHz i5 processor with that upgrade). Any experience with the Fusion Drive? I've seen some older posts (in the 2013s) that it had some problems with file corruption. Nothing reported recently. But, using Time Machine backups, I could recover a corrupted file, if necessary. Any advice here, I'm heading to the Apple store when it opens in a couple of hours.
One more question. I assume I can use Time Machine to move my data files from my 2011 MBP to this new iMac? Someone told me that I can also move my Apps that way. Are there any problems in doing this. I'm keeping my MBP and want to have the same files on both computers (at least to start with, won't try to keep them the same after initial setup).
Thanks for your advice. You both have more experience with this stuff than I do!