bowtie58

I know this is a Chevrolet forum, but my daughters 2002 Grand Am GT, is almost a Chevrolet. It has the 3.4 liter V-6.
She has been experiencing oil getting into the antifreeze. No antifreeze is getting into the oil.
She took it to a local garage, where they said the intake gasket was leaking, thanks to that Dex Cool crap. So they replaced the intake gasket.
She is still getting oil into the antifreeze. It gets in her overflow tank, so she can see it.
Unfortunately, the place she had the work done, has closed, so I will be doing the work.
I've been reading forums on this subject, about the head and intake gaskets going bad. So going to replace the head gaskets.
I'm wondering, if a person has to have the heads planed, before installing the new head gaskets. It's never been overheated, and still runs fine, except for the oil in the antifreeze.
Any comments or personal experiences with this problem, and what did you do, or have done. I will be doing this very soon, and am wondering if the planing of the heads is a waste of money, or a good thing to do.
Thank you to all that have a good comment or suggestion.