The leak I can't help you with. Is your trailer new? The hot water tank should have a 2 year warrantee on it so it should be covered.
How may times did you try to light the water heater? The unit will try to start on gas 2 or 3 times then shut down if no flame. Typically, in the spring the first time a light the water heater with gas, it takes me 3 to 4 times of turning it on until it finally light and the flame stays on. My water heater is in the back and I figure it takes some time to get the gas flowing.
Also, check the orifice for dirt or spider web, which will also impact the water heater from starting. Spiders are attracted to the propane. Clean it out, if needed.
Mary & Tom (aka Hutch)
2015 Jayco Eagle Premier 361REQS
2014 GMC Sierra 3500HD 4x4 CC D/A
Sunlines: 2005 Solaris T-280SR; 1999 Solaris T-2670; 1998 Saturn T-24A