As far as exporting, this has some step by step instructions:
http://bitcoin.stackexchange.com/questions/4203/how-can-i-export-the-private-key-for-an-address-from-the-satoshi-client/5933#5933 :
click on 'help' in the menu bar (top right)
click on 'debug window'
select the 'console' tab
type: walletpassphrase "your walletpassphrase here" 600
type: dumpprivkey [your Bitcoin address here]
this will return the private key, you can copy it now; ensure you clear your clipboard/history afterwards
If I may suggest a slightly different approach. Instead of dumpprivkey [your bitcoin address here] use dumpwallet filename
This will create a file with all your private keys you can easily import into electrum. You import into electrum via:
File -> New/Restore -> pick a name -> select Restore a wallet or import keys and Standard wallet. -> put your private keys in the box (one per line remove the comments that came with the export) and follow the rest of the steps (set a password, let it sync).