My ABS light is on constantly now, I am pretty sure that it means the ABS has failed. Is this true, and if so do I HAVE to get it fixed or can I just drive it as is for a while? Any other problems that could cause the light to come on?

Check the brake fluid level first. If its the wheel sensor you could run without it for a while.

The parking brake sets that light on too. Check to make sure the brake is as far up as it can be.

Also, a loose/corroded connection of the wire at the wheel can set this light off.

Check your fluid level. If its fine... unplug the sensor on the side of your Matercylinder. That should do it. Mine did the same thing.

it also could be a short or grounded wire

You need to retrieve the ABS codes, if you can't find a disconnected wire at the wheels. Unfortunately you can't find a reasonably priced scanner to do it, so you may want to pay a shop to pull the ABS codes.