Do I have to remove the regular Bitcoin Core wallet first? When I try to install the ABC wallet it says data corrupted do you want to re synch? That means it's probably trying to use the BTC block chain?
No, you don't need to remove Bitcoin Core. Bitcoin ABC (by design) attempts to usurp the data directories that Bitcoin Core uses... it was a crass attempt at "taking over" when BCH was first launched and seems to be getting worse.
When installing Bitcoin ABC, be VERY careful about where it attempts to install itself. By default, it will attempt to overwrite Bitcoin Core in the "Program Files\Bitcoin" directory... and also try to take over your Bitcoin data directory when you run it.
The latest version seems even MORE determined to do this... a fresh install of 0.16.2 does not even prompt you where your data directory should go, it just automatically tries to use the Bitcoin one defined in your registry, even if it is in a custom location!
I would recommend that you copy your Bitcoin Core "data" directory (the one with the wallet.dat and "blocks" folder) to a separate location, then delete all the blkxxxx.dat and revxxxx.dat files that are number 951 or HIGHER... and point Bitcoin ABC at this new data directory using the
-datadir=path\to\new\folder commandline argument...
That should put it before the fork, and ready to sync up just the BCH portion of the chain.