I'm pretty confused. If I had bitcoin in a bitcoin core wallet prior to the fork, does that mean I can send those bitcoins now and still claim the bcc later? what happens if I receive new bitcoin in my core wallet now - does that change anything?
Yes, you can claim them any time, today, tomorrow or next year (if it survives that long).
New transactions will be ignored by BCH network.
As of now most wallets for BCH are still seeing "after fork" transactions, Im sure it will change soon.
When a correct network is set in the wallet configs, those incompatible TX's are gone.
Make sure to follow the procedure as stated by theymos in the upper "news bar".