I'm pretty sure I have a blown head gasket do one of those $100 additives work?

the reason I've concluded as such is because my radiator fluid is turning brown...from what I've read this is a common indicator...how about some actual real feedback about these additives and their efficacy...I need some honesty not flippant answers...as you can figure this is a very desperate situation to be in...I'm looking for real help here...or how difficult is it to replace a head gasket myself?