two issues: P0404 & head gasket

hello everyone;

1997 SL1 SOHC. standard xmission.
approximtely 130.000 km (i live in toronto, canada, which is metric)

issue a) giving erratic P0404 SES when engine gets hot.
i have obdc diagnostic tool, which lists a MUST to change egr valve.
previous posts in this forum (btw, excelent forum !!), mentioned an
ELECTRONIC egr, and a possible alternative of cleaning existing egr
to avoid exoenditure.
a parts vendor ststes that no electronic egr valve exists for saturn
(?).
i am confused.........please help with clarification.

issue b) oil stains in driveway.
mechanic have been pointing to spot where leak was taking place (with
some spry and light). he was advising to postpone as possible.
this is THE BEST CAR I HAVE VER HAD IN MY LIFE; and want ot make it
last !!! (also, i am aretiree, and every penny counts now !!)
QUESTION: does the repair / new gasket replacement REQUIRE the block
head rectification ??
(even at U$S values), what amount of expenditure woul i be facing to?

thanks in advance for all you help.
bst regards.

danielR.