1988 Olds ninety-eight issues

I'm slowly losing radiator fluid and there is also a wee bit of oil in the radiator itself. I think that means head gasket right? I can't think of anyway else that oil would get into the radiator. I have a very small oil drip under the car so I don't know how much oil is going into the radiator but I don't loose much between oil changes.

Also, I don't loose much radiator coolant either, and it's not leaking from anywhere, so if it IS getting into the cylinders how is that going to affect performance? What are the symptoms there?

One other thing. My Chilton book says that I'm suppose to change my head bolts. Something about Torque to Yield. What does that mean? They shouldn't be re-used then?

Thanks in advance for any advice.

torque to yield bolts usually aren't torqued to a set torque number, you tighten them to a low torque number then turn them like a 1/4 turn then another 1/4 turn or amount the book calls for. when you do that the bolts stretch some and the elasticity of the bolts keeps the head on tight. when you remove them they may not shrink back to original length so if you reuse them they can snap or not have the elasticity they had when new so they want you to replace them