05 Cavalier Gauge issues

My daughter called me today to ask me what she should do. Sh had just noticed a few minutes after starting her 05 Cavalier that the temp gauge was into the warning portion of the indicator. She pulled over and turned the car off and the gauge still read above the "off" position so to speak by about 25%, she restarted it and it was then in "normal" range.
It seems the speedo hasn't functioned correctly in quite a while.
A google search pulls up what appears to be a lot of people with similar issues with the cavalier gauge cluster but no real resolution other than pay the dealer $500 to fix it.
I told her( boyfriend) to disconnect the battery for about 10 minutes and see if that has any affect on the gauges. I also asked him to check the fluid level in the radiator, told him to pick up a hydrometer to check the gravity.

Can anyone enlighten me as to the issue with these vehicles and perhaps offer a suggestion or to that could fix the issue( i did read somewhere about replacing the step motor..about 3.95 each)
Thanks for any direction.

Without disconnecting the battery or checking the rad fluid, the next day the temp gauge seemed "normal" speedo still doesn't work.

What is the coolant level?

Could be two seperate problems...

Speedo problem could be a VSS/wiring problem....

im having her check the coolant level
vss....variable speed sensor? how difficult is that to replace...what about cost?

A little update for what it is worth..the odometer still works even though the speed is not.( not usre if at all or incorrectly)
She is 1700 miles from me and has about a 65 hour a week workload, s communication is sometimes slow.

Ok so ,as it is, the speedo hasn't read correctly for some months..6-8, sometimes it sits at 0 sometimes it sits at 100 more often than not it just jumps around.
The fuel gauge very often read way above full, even when it is not, sometimes way below where it should be when filled up, sometimes it appears to be correct.
The temo gauge has been normal since the original incident, she hasnt be able to check the rad fluid levels yet :nono:..im trying to get her to do that.:banghead:

So is it likely the gauges just need to be repaired? I see quite a few links to places that do full GM gauge repairs for about 75 bucks. ( remove send in and reinstall)