If I understand your description you ....
- have a CS2
- it powers up
- but the screen is dead (not sure if this means unreadable or where the touchscreen part does not work)
- do not want to leave the CS2 connected (as slave) to the CS3 in order to continue to use it for its memory capabilities.


If the screen is readable, and it is the Touchscreen that is faulty (or needs calibration), then you would be able to add a USB mouse.
(While you may use the mouse to navigate and start the calibration, do not use the mouse for the actual calibration - use the touchscreen)

If the screen is unreadable only (please confirm that the Stop button works - also if you have a LocoCard, please use that and indicate if the throttles and tactile buttons work).

If you are able to connect to the network (ethernet cable) you will need to ascertain the address of the CS2.
Assuming that the address is either DHCP negotiated or you have specifically set it for the same subnet as your PC, you can use a browser to point directly at the URL and use that to retrieve some information.
Two functions that may be of interest are
- the "ScreenShot" function which will show what is , trying to be displayed , on the CS2 screen
- access to configuration files.
- - specifically http://***.***.***.***/config/fahrstrassen.cs2 which is a text file showing your memory routes.

The files are "structured" but may be read and interpreted with a bit of perseverance.
(I usually parse it to a spreadsheet and run a macro to improve the layout. although it is also possible to do this with an app directly from the CS)

While the memory routes cannot be transferred directly to the CS3 events, at least this file will provide a document from which you can work from to redefine the routes.

Note: there are some things that CS2 memory routes is able to do that CS3 event cannot, or at best have to be done a different way.