95 Monte problems

I had to replace the alternator in my Monte, and since then, it has been nothing but problems. After sitting for a few hours, the battery is dead. Not realizing it may have been related to my alternator, I replaced the battery.

The wiring, fuses and connections have all been checked. I also noticed that a red blinking light for my stereo no longer comes on - could this be related?

This has been very frustrating!! Help!