coolant problems

hi everyone,i`m new here and i`m glad that i found this forum.i know this question has been ask often,but i need additional info.i have a 1998 lumina and i`ve been adding water daily for the last three weeks now.when i first start it up in the morning i hear a tapping sounds now also.it still runs good but this morning when i check the oil water was in it.i also pull the oil cap off and there it was ,white gunk on the top and inside the cover.can someone tell me what kind of gasket do i need.and if its the lower or upper intake manifold gasket or the head gasket and is it a hard job to do.thank to you all in advance for your information

I had the same thing happen to me. I was sitting in traffic due to damn traffic and the car began to overheat. I couldn't move, so I was forced to sit in the traffic.. The engine got so hot on the way home (had to drive it cuz I couldn't pull over due to traffic!) that it burnt the transmission slap up. The car wouldn't even pull in the driveway, and I had my foot mashed on the gas.

I took a wild guess and thought it might be the lower intake gasket, which I was correct. It took about a day to dismantle everything, then another day to install everything back together. It's not that hard, but it's down at the bottom of the engine in the lifter valley. It's a good expierence tearing it apart and putting it back together. If you attempt it, I'd suggest getting a Haynes manual so you can find out the torque specs and teardown instructions (if you haven't done this before)