My 2006 Sonata won't start
 

I have a 2006 Sonata v6 which I believe the exhaust froze. I put it in a heated garage to let it thaw out. Now, the engine turns over fine, but it won't start. I'm not sure if it's flooded. I did change 3 of the spark plugs which I could get to easily. I couldn't locate the other 3. Any suggestions? Thanks.