you need to change the resevoir soon. the crack will get bigger, and because the system pressurizes, you will start losing more and more coolant.
on another note, i just bought a really nice used heater box, with the heater core in it. and those "quick disconnects" are a beyatch even with the core out of the housing. i never changed them on the car, i just pulled or cut off the heater hoses, and left the pos quick disconnects still on the core. what a dumb idea, thanks ford. i have a nice set of 18" needle nose pliers, and another 90 deg, and they are great for the spring clamps. i now prefer the factory spring clamps over the screw on type, and i have been scrounging up spring clamps to put back on when i am in that area. you should change out the breather hoses, too. i know one of them is now nla.