boybitz/cesar,

valve seals can be replaced either by top overhauling or pwede rin sungkit/dukot... though if ur engine is due for timing belt/chain replacement, isabay mo na rin, para isang trabaho na lang...

on the side note, kung may langis ang sparks mo maraming pwedeng cost nito... I'm having the same problem recently, and after a lot of elimnations, we are down to 3 culprits...

1. Busted valves
2. valve guides needs replacements
3. Piston ring needs to be replaced...

I've changed my valve seals (valve stems) twice for this month... and it aint cheap.. btw, AFAIK the number of valve seals depends on the number of your valves, if it is 12, then 12 and 16 if 16...

Oily sparks leads to higher fuel consumption, bad smoke emission, loose compresion, and also if neglected, lost of oil... and you know what happens when u loose oil...

anyway, if ur having it check and replaced.. look for a reputable mechanic/shop for that... remember, ur having ur car's heart is treatedn here... :lol:

HTH