Yes, the seals are easy to change, and sometimes will help. Many times though, the guides are worn and replacing the seals doesn't accomplish much.
The key is bronze wall guides. When it comes rebuild time, use bronze wall guides. Small block Chevies have always been tough on guides. The bronze wall is basically a bronze heli coil that is put in place then reamed to size. They will stay tight for a long, long time.
It is not necessarily the valve guides all the time. I had the same problem before I did a major preventive maintenance program on my car. I changed all the sensors, cleaned the IAC and its port, adjusted the TPS , changed all the filters (air and fuel) changed the PVC and changed all a vacuum hoses, plugs, wires, coil…ect. Now I start it up and clean a as whistle. I passed emissions with nearly a perfect score. Check the color of the smoke.
black = excess fuel
white = water or coolant
bluish = oil