2000 town and country head gasket

I recently had some work done on my van. just regular maintenance. the
mechanic told me to keep on checking on the coolant as he says i
could be in for some head gasket problems. what should i be looking
for. my wife drives this vehicle most of the time . the only time i
drive it is when it needs some gas or an oil change or taking it to
the garage for maintanence., i have a feeling that getting the gasket
replaced is a big job. what should i be doing in the mean time to get
ready for the eventual breakdown. can it be prevented
all help will be appreciated ...cheers