is it safe now to use the light wallet for claiming and regular use, or is it still not a final release and intended just for testing?
At the moment i know 2 people that successfully claimed with the light-wallet (1 on linux and 1 on windows). I never heard of a problem with claiming

Its really easy:
Go to "Tools" and click "Claim Process"

Then simply enter your old seed and a new seed. Wait until PoW is finished. Login with your new seed

Take care of your seeds! Make sure you dont lose them in any way (create backups, print them or do whatever is needed that they dont get lost)