How do I export the private key thing?? After importing that key onto a lightweight wallet, can I just uninstall Bitcoin Core.
Thank you all for the help btw.

you just have to drag your wallet.dat into blockchain.info then you'll be able to use your bitcoins.
find your wallet.dat file in appdata folder and open up (
https://blockchain.info/wallet/import-wallet) then drag your wallet.dat file and start using blockchain.