and you know that this is an engine problem right? ask them if they did this:

compression test on both cylinders.

check carb.

check air filter.

there are only four things required for a motor to run. compression, spark, gas, and air.

so, if it's not getting one of those things, it needs to be fixed.

but, if all of those check out ok, then I would say you need to look at the hydro system, and the blade drive system.

if the engine runs, there is NO reason you need a new engine. did they tell you what is wrong with it? if they didn't tell you, and they just say "it needs a new engine" then you are getting ripped. I had a dealer try to do that to me, nothing even wrong with the engine, just a blown oil pan seal. sheesh.