http://amiga.resource.cx/exp/egs28 have the install software. For the manual: good luck!
I think it's better to use the 28/24 inside the Indivision, so you can have the best of two worlds: a RTG Amiga (EGS) with custom AGA modes (Indy). You need to make a custom cable, but that's dead easy.
You'll find your Amiga running blazing faster when in Picasso96 or CyberGraphicsV3/V4 modes and with almost all precious CHIP RAM free.
The Indy will be come in handy for games and to hook a modern VGA or TFT/LCD screen to the Amiga.