Replace V belt on Sears Riding lawn mower

We have a new Sears riding lawn tractor that has been broken down more
than it's worked since we bought it.

first they had to replace the engine (they said) because "someone" put
the air filter in wrong and the engine locked up. Then the battery
died. They replaced it with a new one. It died because "someone"
forgot to hook up a wire so the battery didn't recharge.
The next time we tried to cut grass the same thing happened again and
the battery was dead. (They can't even be jump started) so they came
out, replaced the battery again and said it was because a DIFFERENT
wire wasn't hooked up.

we cut grass for about an hour after that and the blades stopped
turning. the belt is off the pulley and has a big chunk gone out of
it, so it will have to be replaced.

It's probably still under waranty, but unless it's a really difficult
job, I'd as soon buy the part and fix it myself as wait around another
week or two before they come out and "fix" it. Meanwhile the grass is
getting higher and higher.

anyone know how to replace the belt?

Thanks