If you really want to make it a DIY project.
Use an I-Pac or KeyWiz. Wire it up to send a key command whenever the puck slides down the chute for a goal. A
cherry switch with an actuator would be suitable for this. A quickie VB program can be used to keep track of score and such.
For signage, you can Google for a variety of methods of displaying scores and other data. I spotted one modification that used a LED-Wiz to output to a LCD display. With careful wiring and an LED-Wiz' or two, you can accomplish the same thing using numerical LED displays. Or you can get really fancy and use a couple of very small monitors to display a score, that would go well with a custom VB interface.
It's just an idea. It might be cheaper to steal the electronics from an el-cheapo Wal*Mart topy, but I don't think it would be as flexible or fun