Gm stopped using or recommending them in early 2000s. They were meant for nuisance seep leaks. All they do is turn to mud and start plugging stuff up. I flushed half a pound of that crap out of my system I bet. So no don't use them.
General Motors issued a TSB (Technical Service Bulletin) sometime in the middle 2000s that removed the requirement for our cars to use the sealant tablets or powder (Bar's Leaks #HDC or G12BP)
Those bulletins, as well as engine oil advice, are contained in the appropriate sections of the GM service manuals in the website www.alldatadiy.com.
Alldata is updated for technical papers; the paper service manuals are not. My 2002 GM/Helm service manual set is dated "Second edition, 02/2002". My Alldata subscription to the same manuals for the same car contains TSBs up to 2013. (EDIT: TSBs to 09/2014)
Rickou, Please study the several sticky posts on the Engines; Northstar main threads page as well as the entire Cadillac Technical Archive up in the very top ^^^ black bar.
p.s. - I have performed 3 complete coolant exchanges on my 2002 and have never used a tablet or powder. No leaks, either. This 2 quarts of DEX-COOL came out after 3 years - this is what ALL used coolant should look like.