My 99 forester just had head gaskets replaced and now there's an oil leak coming from the crankshaft seal on the front of the engine.How difficult is this to change and what other things should I be looking for?its a 2.5 s.o.h.c engine

You just learned a lesson the hard way. When you have the front of the engine apart replace all the seals. Usually if the seals havent been replaced, the timing belt idlers havent been changed.

 

Normally you would do cam seals (check to see if they were replaced), main seal, re-seal the oil pump, replace the water pump, idlers and the belt. You have to go over your HG list and see what was replaced and what wasnt and act accordingly. If in doubt replace it. Also replace the PCV valve, and generally a good idea to change the oil after a HG replacement if the engine ran hot. Also the car is old enough for a new OE thermostat and a radiator cap (any mfg).

I went back inthere and replaced the seals and no more leaks as of now,timing belt was done 40,000 ago so i left it alone looked to be in good condition i now have a p0420 code to diagnose

Were you burning coolant before the HGs were replaced?

 

i now have a p0420 code to diagnose

this is usually an o2 sensor issue.

but there can be lots of different causes, including an intake leak.

 

there is a great posting over on the outback forum about htis.

extremely informative.

 

http://www.subaruoutback.org/forums/66-problems-maintenance/49537-p0420-diagnosis.html?highlight=p0420