Put it back together and try to return it for a full refund of your money. Simply removing the cylinder head may void your warranty, however, you probably didn't damage anything in the process.
We had a Weedeater riding mower in the shop for over a year waiting for a warranty transmission and when we finally got the replacement in and installed it, the new transmission had a different problem and now the waiting game starts all over. Needless to say the customer isn't happy. My advice is to stay away from anything "Weedeater" brand. I told this particular customer that "you don't get what you don't pay for".