Who told you they need work in the heads? They almost never have an issue, especially since the 1998 casting update. A lower intake gasket failure of the coolant ports is the most typical issue on these, since the iron block and heads stay sealed up very well.
There's tons of YouTube videos on how to dig into 3800's for various work. Get your diagnosis squared away (compression check, vacuum leak check, coolant pressure test), so you're only digging in as far as necessary to save money. If this is beyond what you want to do, then the rest of the work required isn't even a factor.
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