Nah. You'll end up doing a better job. At least on my 60 I had to mess around with it a bit to get it to be stable & look decent. Many of those installers can do OK with a slip in & slip out install. But if you have to mess with it ...you'll have more patience than they will....it's your...
You probally could do it with the dash still in the truck. But it is much easier & you can do a better job with the dash out. I just bent those metal braces inwards (both of 'em) & slid the radio in there using the metal braces as sort of a spring tensioner & then supported the back with...