Driving with very small crack in head?

I think I may have a very very small crack in my head on a 3100 v6 between cylinder number 1 and the water passage. Slowly I notice grainy sand like stuff in the overflow tank with almost no noticeable water loss, car runs a tad bit rough and the coil pack that fires that cylinder did go bad but the car had 100k miles on it. I have a friend who has been driving a ford truck for years with a cracked head and he says he just adds a gallon of antifreeze every year. So the question is, is it ok to just not worry with it since it doesn t appear to be a big issue and head repair is expensive.

note, I have changed the intake gasket and no water is present in oil
Added (1). car is 96 buick century wagon
Added (2). thanks everyone, I flushed the system very well when I changed the intake gasket then filled with universal coolant. I am going to check the plug, the coolant probably looses a millimeter after 500 miles, its so very slow. Car runs well but just doesn't idle like a new car, plugs and wires are new, crank and cam sensors replaced also MAF MAP and TPS, I will check the plug and if it looks good I will not worry
Added (3). car usually runs very cool oddly, it runs at the 1/4 mark but when sitting it reaches 1/2 but then cooling fan comes on and brings it down. I have taken 3 hour round trips in it and it seems to be trustworthy but would like to verify head
Added (4). due to the fact that the elbow hose blew, the car overheated and ruined the temp sensor, when trying to remove temp sensor it had been cross threaded and broke the intake so I replaced the intake and put the good quality gasket in. So the overheat has got me worried, it seemed to run a little smoother before.
Added (5). car never throws misfire codes which is strange to me, even when coil pack died and left two cylinders with no power, no codes, maybe first gen obdii did not test for this
Added (6). I replaced the crank sensor on the side of the motor that runs to the ign module, not the one by the crank pully

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