roof A/C clean or replace?

[maseratidoug]

I bought an older TT and when I wanted the airconditioner in Arizona it didn't hardly blow even cool air.  I've seen the cleaning video, but my question really is is it worthwhile to make the climb on the roof and do the cleaning job?  And I'd heard that if your trailer doesn't have a ladder that means you shouldn't be getting up on the roof, is this true.