Toyota Repair: how long to replace rear oil seal on 92 Corolla, valve cover gasket, pan gasket

Question
Hi Ted. About how long would it take a professional mechanic to replace the rear oil seal (camshaft seal?) on a 1992 Corolla? I thought my transmission pan gasket was leaking, but it turns out that it is the oil leaking from the rear oil seal (camshaft seal)onto the transmission and down the transmission pan. Is it a major job? About how much would it cost at a local repair shop? If I don't fix it, would the leak get any worse or just stay the same? Thanks!

Answer
There is only one camshaft seal and that's on the front of the engine in the cylinder head, if the leak is at the rear of the engine then it may be the engine rear main seal, replacing it would require transmission removal, this can easily take eight hours to do.
If the oil is coming from higher up then it may be the valve cover gasket and the camshaft plug, which is recessed into the cylinder head, to replace those should take about an hour. At the same time the distributor O-ring should also be replaced.