Just use whatever antifreeze you want...if it already has green coolant, stick with green though. The green and yellow coolants do NOT mix. So, if you plan on switching to a yellow coolant, you MUST ensure you flush out ALL of the green stuff...
Other than that, make sure you refill the cooling system properly (via the burp plug, near the alternator) and "burp" the system of all air after you finish.
No need for any additives....
The owner's manual should list the capacities for the cooling system, trans, and pumpkin.