I bought my house about 5 years ago, and it already had an alarm
installed (wireless sensors, motion detectors, and a very annoying
voice that screams "SYSTEM IS ON" and "SYSTEM IS OFF," etc). I'm
guessing that the alarm is about 10 years old, but it could be
slightly more or less.

Recently, the keypad decided to go screwy. If you hit a key (any key),
it just beeps incessantly. Not beep, beep, beep, but
BEEEEEEEEEEEEEEEP. At first, you could press a bunch of random buttons
and it would eventually stop, but the last time it went off I couldn't
get it to stop so I totally unplugged the keypad.

Which, incidentally, doesn't make me feel all that safe.

Assuming that the problem here is just the keypad, can I just buy a
new one and plug it in, or do I have to replace the whole kaboodle? If
so, are the plugs pretty much universal, or will I have to rewire the
whole thing?

TIA,

Jason