HI! I need to replace the old AM FM cassett radio in my 86 345 but do not know where to start taking the dash apart in order to get the old one out and the new one in.  I have purchased new Ultraleather for the dash mat and so I also need to remove the old mat without tearing it up since I need it for a pattern. As with other posts I'm tickled to find this site....AS trailers just do not have the same problems and fix its that a MH has and so the posts go unanswered or with misinformation.
Pete

Pete,
Welcome to the site. We're glad to have you. I replaced my radio (also in an 86 345) a couple of years ago. I put in a Sony XPlod radio with a built in XM jack (no antenna) and it was a pretty easy replacement but did require some cutting, etc.

The dash panel itself comes out with about eight small black screws around the panel edges. You can pull the knobs from the old radio, then remove the lock nuts so it will slide out the back. Once you remove the dash plate screws you can tip it forward enough to get to the back of the radio. It helps if you tip the steering wheel down.

My replacement radio required a rectangular hole for the mounting box. Depending on the replacement you can get on that re-uses the existing holes. I hade to measure and tape and cut a hole in the metal panel using a cutting wheel.

Replaced ours a few years back.  I took it to one of the big electronic stores that offered free installatiion and they did it in short order.  The new unit fit right into the old opening and the mixer plugged right into it as well.  Seemless installation. 

Now we an AM/FM with CD player and XM ready.