Hello,
This is not only doable, but already done.
If you search for "S-Record format" you will see quite a few documentation explaining how to extract info from the the S19.
www.s-record.com is ONE example of good resource.
All info you need is IN CLEAR in the S19.
Also, you can see some Application Notes called bootloaders which re-program the Flash on-board, by receiving an S-Record via a serial port (CAN, SCI, SPI).
Cheers,
Alban.