2006 Suzuki Forenza coolant stain

Took in for transmission fluid change, mechanic found
coolant stains from behine EGR valve, front top of
engine to bottom. Says may be head gasket, t/stat,
or housing.
car was in dealer last month for transmission switch
and they basically forced a serpentine belt on me, because it had never been changed. They did not
mention anything about this.
stain is quite visible on front of engine. What are our
options. Would like to keep car, due to negative
equity. Would be hard to buy new one

thanks