You'll need to take out all of the windshield trim on the inside of the cab - lots of screws. Cutting the gasket would be helpful in removing the glass - and the glass is removed from inside the cab, not outside. (Take care with the glass, especially if you're not installing new glass.) After you clean everything, place the glass in the new gasket (did you keep track of top and bottom of the glass? It matters...) and install from inside the cab. Needs two people minimum. In the Tech section on this site has a pdf version of the mechanic's manual - it has information on replacing the glass as well, it'd be good to read through that in addition to what you get here.