Here's a video of some guys working on an L67 supercharged version of your engine. You wouldn't have a supercharger, but an upper intake manifold though:
http://www.cpaclubgp.com/misc/lim-gasket.html
Here's my experience with replacing my gaskets about 3 1/2 years ago:
http://www.clubgp.com/newforum/tm.as...de=&s=#2714720
Here's a link to a how-to:
http://www.autozone.com/shopping/rep...00c15280217c80
Before blaming the gaskets, take a look inside the UIM thru the throttlebody and see if you see any coolant inside there, if so, the UIM is probably leaking coolant around the EGR, kind've a common issue, with aftermarket manifolds available to replace the entire UIM. You can even find 'em on eBay for not too much $$ (vs GM prices).
Here's a link to available UIMs:
http://www.automotiveforums.com/vbul...d.php?t=701325
If you decide to replace the LIM gaskets, here's a link to the GM aluminum LIM gaskets which are superior to the old plastic ones:
http://www.automotiveforums.com/vbul...d.php?t=700914
Let us know how it goes or if you need further help
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