Volvo Repair: Oil leak, vacuum hoses, flame trap

Question
I have a 1987 240 DL wagon.  Evidently the pvc (flame trap?) became clogged and caused both the front and back seals to start leaking.  I got a new flame trap and for the most part it stopped leaking (I did not see drips on the garage floor).  My mechanic indicated to me it still was just that it as blowing back.  Anyway in the absence of drops and no loss between oil changes I have let it slide.  It is now 13 months later and the leaking has come back, especailly in front.  I am even seeing "oil splash" even on the RF mud shield.  How big a deal is it to replace seals (estimated time and parts)?  Would I likely need to do front and back or just the front.  Should I just try replacing the flame trap again.  He said they should be good for 2 years.  I( would probably do that anyway if I invest in seals.  FYI, the cars has about 150K miles on it and I do not know but don't believe seals have been replaced before.  THANK YOU!

Answer
I would check the flame trap and all its hoses and vacuum hoses to be sure they are not blocked.then I would also do the front seals if they are leakign and look forward to doing the rear main seal.front seals about 3 hours labor and 60 dollars in parts.rear main about 6 hours and 40 dollars for parts.