I just got my car back today, and here is the (hopefully) final word of what was wrong with it. The water pump was leaking, the thermostat was "bad" (the mechanic didn't go into any more detail for me), and the upper and lower radiator hoses were on the verge of cracking. Taking the advice I got on here, I "bit the bullet" and had all the work done before summer hits full swing and I get REALLY screwed.
Also, I went ahead and got the aluminum thermostat housing as a preventative measure.
Thanks for all your advice! This forum never seems to let me down.