95 eclipse spewing oil

I'm new at this. I just bought a 95 eclipse nonturbo. There was oil in the spark plug tube so I replaced the valve cover gasket, plugs, and wires. I changed the oil and filter. When I started it up it ran rough at idle and oil was leaking from the tail pipe. Am I going to need a new motor and if so where could I find a decently priced one?

did you replaced the spark plug oil seals?
you might have bad piston rings. have you done a compression check?