What should I know ? parts are on hand just need to pick some antifreeze will go with 50/50 peak or should I use anything specific ?

About how much time would it take for an above average mechanically inclined person ?

My friend who is a tech tells me its a 3 1/2 hour job I dont see it being so long I did my e39 ( 530 BMW ) in under 2 hours last year and that included the radiator too.

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2003 GX470
1998 E300 3.0TD
2002 Dodge 2500 4x4 cummins
1998 Dodge 3500 5 speed Cummins