Thanks Lumix you're right about that!
2Late, the removal is easy. Just pop off all the trim around the glass, and slowly cut away the seals around the glass.
It is slow, grueling, tedious work.
One that's done you can lever the glass away and clean the remaining seal from the metal.
Once THAT'S done you can check any rusty spots (usually around the glass mounting brackets) and sand them back.
Once clean, paint the entire metal surface which is usually covered by the glass with some POR-15, I did three coats but I dunno if that's necessary.
I paid a guy to make and install the new glass, just helped him position it once he'd prepped the area and laid the new sealant; the glass is so heavy and positioning so important I'd pay him again to be honest.
What location you in?