Oldsmobile/Buick Repair: Temperature gage keeps going up to hot then cools down, then goes up to hot again, oil dipstick, temperature gage

Question
----Hi Pete, this is Diane again. I talked to auto mechanic and he says he thinks it is intake gaskets not the head gasket. He hasn't seen my car as I don't want to drive it only to get it to the garage. Then I got a different opinion from a friend and he said it is not throwing oil out so should be the head gasket. I would appreciate your opinion on this. Thank you for your time with me and your opinion is very much appreciated. Have a good day. ---------------------
Followup To
Question -
My temperature gage keeps going up to hot but then will cool down to about 3/4 which is where it always runs. Sometimes cools down to half mark, but then will go up to hot. Does that mean I need a new thermostate. If so, what does a 1995 Buick century v6 have or how do you replace? I was told 2 years ago I needed new head gasket, but I never used any oil and don't leak. Also it idles very smoothly. But when they added anti freeze they said had to put in 2 qts. and said that oil discolored. Would this make the temperature gage fluctuate?
Answer -
hello hun  this to me sounds like a head gasket the car will run smoth with water in the oil . pull your oil dipstick and see if it looks milky . it is a sure sing then it is a head gasket . And yes a bad head gasket would cause the temp. to rise and lower like your car is doing to you . it would be 500 to 1000 to have this done it is costly on less you could do the repair or have a frend or husband who could help u . i would walk you threw step by step . good luck to u hun and if you need more help please let me know and you do have a pretty name pete

Answer
Hello again hun
No problem helping if you are leaking oil it is a head gasket sure of it a intake would not bother the temp any way . this mech. wants to make money good luck to u again and if you need more help please let me know . and u do have a pretty name pete