My Club Cadet Series 260 walk behind trimmer which has two weeks left on factory warranty and 3 years left on Home Depot extended warranty,  runs bad or runs for 5 seconds then stops. I have cleaned the carb, fuel filter, fresh gas, new oil. I have two weeks on the factory warranty and 3 years on the extended Home Depot warranty. Top of gas tank under plastic cover leaks gas ( It is split on top of tank)  all over tank at 80% full. Factory Dealer says to put up a $200 deposit and can't look at it for 2 months. Home Depot won't look at it till factory warranty expires in two weeks. Advise??

Well, If you can't find water / crap in the fuel, sounds like a warranty issue.
 
I suspect the deposite is to cover if they found water/etc (owner induced issue) which wouldn't be covered under warranty.  You should get that back if the machine is found to be defective.  
 
A cracked fuel tank sounds like a warranty issue itself.
 
I'd rather have the shop check it vs HD myself.  
 
Just curious, what engine is on it?