I forgot to mention that you can't update the bios for the Compaq. Compaq doesn't support that motherboard and it is a proprietary bios (not Award or AMI).
You old monitor will be fine. Monitors don't have speeds, they have bandwidth and if you have a monitor that works at 1024x768 with a refresh rate of > 60 Hz, then it will still work on the new card at that resoluton and that rate.
Your keyboard and mouse will also work fine as will any CD Rom drives/DVD drives, Floppy drives, Network cards, Sound cards, etc. (as long as they are PCI). I only bought the mobo, case, psw, video card and memory and am using everything else from the Compaq.