Not Power steering fluid leaking!!

Hi all..I had my new 2nd hand lenses fitted today by my local mechanic..great job at bargain rate...but I had earlier spotted an oil leak(and smelled burning oil/rubber while sitting in traffic) that I thought was AFT fluid as my reservoir was always leaky/wet and the oil I could see was like the oil in my reservoir...manky and brown. A whine rattle I heard briefly made me think the powersteering pump was giving up the ghost...until my man tells me it's not but the only place leak might be from is the head gasket. Now when I was putting the car back on the road after sitting up for 1 1/2 years the thermostat stuck and car overheated(but I didn't drive it far) and shortly afterwards the bottom hose on the rad popped off...causing an overheat again(didn't drive car v far then either....200 tards perhaps) both overheating issues were sorted, and gauge is right on the button for the last 3 months....buuuuut...my Q is...is there a gasket treatment additive I can use to help me along. My mechanic says tisn't much of a leak and says keep an eye on engine oil level. Any suggestions are welcome and really appreciated as before. Con:surprised::sad::sad: