Yeah redlines are there for a reason. YOu can bump it once in a great while and on some cars it's no big deal. But apparently the LS is a tad touchy. I am of the opinion this engine is just too small and overworked, but then I am one of those old American iron Big V8 lovers. Have a nice 460 right now, gulping down 11mpg, owwww.
Keep this in mind. I. E. my experience is with old tech V8s using cam in block designs. I haven't ever had a really big problem with DOHC type engines since I was older and less inclinde to mash it by the time they became common. So I may not know what the heck I am talking about in the following.
Anyway. When you hit redline many different things may happen. The most common problem is that the valves will float. I think this is still possible with DOHC engines. Or in extreme cases the piston rods will stretch just enough. When this happens the valve may kiss the piston and depending on how much interference there is, it will either bend the valve, break the rockers, break the cam etc. Usually just a bent valve, which does need to be replaced before you drive it much longer.
Occasionally, usually on an old loose engine, you might over stress the piston rods and either break it, which is obvious, or you might damage the bearings, which is less obvious but may cause some knocking. I suppose the bearing might squeek but I have never had one do that(even with severe bearing damage), but I have only played with maybe 20 engines in my lifetime.
I am guessing the squeek is something from the belt drives and probably just something you noticed because now you are paranoid.
Other possiblities are some knocking from the tranny due to some damage which I am almost totally unqualified to talk about. Or possibly one of the components on the belts is knocking. Some AC compressors have a redline too, and when you exceed it it can be damaged. To check for problems with things like AC, alternator, powersteering, just remoive the belt and run the engine. If the noise goes away, then it isn't the engine and lucky you.
By the way, oil at min is not always the best thing when mashing it. At high RPMs, sometimes the oil is all in the top of the engine and none of it is getting to the crank bearings. If you lose the oil pressure due to sucking air at high RPM, you can quickly damage a bearing. I forget the calculations but the guys on the SHO website have a good tech article about oil starvation at high RPM. Like I said, essentially the oil pump pumps all the oil up to the top of the engine at high RPM and because it takes time for the oil to get back to the pan, sometimes the engine will suck air. Low Oil level just makes this happen sooner. Hope this ain't your problem.
Good Luck, this is one of those lessons from the school of hard KNOCKS, like you got, sorry for the pun.
Jim Henderson
We were going back and forth for a little while, and I red lined quite a few times (its an automatic, so it shouldn't have gone further). When I got home I noticed that my engine was knocking. I turned it off and let it sit, thinking it would go away after it cooled down. The knocking hasn't gone away and it sounds worse. There is also some squeaking when it idles. 
