often it's the front and rear crank seals that have this issue. If the leak isn't too bad - just checking the oil level frequently should be good enough (for a while). If you want to have them replaced by a shop - the one in the front needs the timing belt to be removed, so figure $400-$500 (most of this cost in labors). The exhaust + tranny needs to be dropped for the real seal - so some more labor costs there as well.
Most try to cooridinate doing with a new timing belt job and a clutch job -- to keep costs reasonable.
FYI: Timing belt needs to be done at 60k and 120k miles -- so something else to consider when buying this car.
