Fast Idle issue and Oil Leak

I just had my carburetor replaced on a 1970 Nova V-8. When I was driving it last night I kept noticing that it wanted to go into fast idle mode. When I would tap the accelerator it would kick back down to normal- but once I started driving again and accelerating I could tell it was idling high again as would become obvious when I came to my next stop. Is there a screw that can be turned to adjust this? It’s a Holley Carburetor that was put on- the one that was on there before was a Rochester and that one was replaced because the car was having a lot of difficulty with cold starts. Also it just had an Oil Change and I have noticed twice some oil near one of the valve covers. My mechanic called me and said to turn down a screw on the passenger side and that the oil issue he looked at and thought it was resolved- I guess it isn’t yet. Have I bitten off more than I can chew? I have only owned the car about 6 weeks and have put close to 2 grand into repairs so far.