You can get programs that display system temperature information, but only if your motherboard has built-in sensors. Check the mobo manual for information, since most that do come with a utility on the mobo driver disk.
You can also try this program.
http://www.snapfiles.com/get/hmonitor.html
It also checks fan speed and PSU voltages, although there are plenty of other programs out there.
edit:
I've tried a blow hole on my old case, and I couldn't believe how much of a difference it made. To be fair though, it was an old AT case that I'd modified extensively. Most new cases are designed well enough not to need them, but you might want to try it anyway.
Also, how did you notice the temp on the CPU was high if you don't have a monitoring program.