Readdy to do my upper intake, few questions

I'm ready to do my upper intake on my 1997.

After research, I decided this one was the best, at the best price.

http://http://www.automotivepartsnetwork.com/store/pc/viewPrd.asp?idproduct=229679 (http://www.automotivepartsnetwork.com/store/pc/viewPrd.asp?idproduct=229679)

This one comes with "… it includes everything you’ll need to do the job right!"

I remember someone posting that something breaks when you take the old one off. A reminder was if you where doing it on a weekend, make sure you have this part, since they will be closed. What is this part, and does this kit come with it?

Also, People say when you take the Plenum off, since your right there, do the lower also.

Although you are "right there", it does seem to be a lot more involved. Remove Belt, Alternator, price of the gasket, scraping the old one, stuff like that.

Can someone help me balance out doing both or just one? How likely is the lower to leak? It's not plastic. Why do I need to replace it? Is there a problem?

Thank you,
Chris.

That kit looks good. Note that you will need to remove the old EGR stovepipe (visegrips work well), and chances are the replacement will be a little loose and need to be glued into place using a HIGH temperature epoxy (i.e. at least 500F).

As for the lower intake manifold gaskets, yes I agree that now is a good time to replace them. There is a very good chance that they a falling apart and if you do need to replace them in the future, you will need to remove the upper intake manifold anyway. The gaskets are made of plastic and become brittle and collapse into the coolant channels in the heads. It is more work, but if you can put off the work until you have time to do both, I would very highly recommend it to you. You only need the gaskets (felpro ~$50, or GM supposedly makes metal ones) and a new coolant elbow, as it will break when you remove the LIM.

Good Luck