Short round one at the bottom of the board, is the motherboard Real Time Clock battery.
The Simdisk is one of the long boards (off the top of my head, the third board over, from the left) secured in place by a screw at the bottom. I had to remove one ribbon connector, and a two conductor lead marked "keyboard" to access the simDisk board. If you look at it's surface with a flashlight, pretty much the whole thing is little rectangular IC chips. About half the SimDisk chips on ours had paper labels marking the version on them.
The battery is located at the same end as the screw and retainer plate/bracket thingie on the end of the card. It is a black rectangle without any "legs" out it's sides. The polarity is marked, as is the part number and name, as per my last post.
From what I could see, the changeout will require desoldering 4 points, two of which are the terminals.
LTC-7P Eagle-Picher | Mouser Canada
Cheers
Trev