After connecting to a liquidity swap, can I use (spend) the sats that I used to create the channel?

Fees used to create the channel are paid to the miner of the Bitcoin block which records the opening of the channel. You will no longer have those sats to spend. Assuming you created the channel without pushing sats to the remote end, you will usually be able to spend ~99% of the sats in that channel except for the ~1% allocated to reserve. There are exceptions for very small channels as the reserve must be greater than the  dust limit, currently 546 sats.

Learn more here: https://github.com/lightning/bolts/blob/master/02-peer-protocol.md#the-open_channel-message