Bob, simply injecting resin into a delamination void has zero chance of
holding up... Ditto for riveting aluminum strips to the lower cowl...
You need to use a good grease cutter on the oil soaked areas (simple
green, 409, etc.), followed by several scrubbings with liquid dish
detergent and water, followed by spraying MEK on until it runs off
(don't use bare hands for this stuff as it absorbs instantly through
the skin and goes straight to the liver)
Then you need to grind away the surface of any delamination (from
either the inside or the outside depending on which side is the thinner
part of the delamination) until you have removed the bad stuff and have
a good layer left... The edges of the ground out pocket need to be
tapered/scarfed to at least an 8:1 slope... Then you need to build up
the removed material with unidirectional fiberglass and epoxy resin...
Check the archives at rec.aviation.homebuilding for pointers on this
(the Cozy MK-4 group is a good source of information)... Also, boat
builder chat groups and personal web pages will have pictures of the
proper way to layer the glass in, etc.. Lacking that, ask around for
the local EAA chapter and someone there will speak fiberglass
fluently...
Also, the bottom lip needs to be ground back to solid material... The
edge needs to be scarfed at an 8:1 slope... Then using .032 aluminum
make a form to clamp to the cowl for shaping the new lip... Put a piece
of saran wrap on the aluminum as a release layer... Then lay up new
glass layers...
Your surmise about non airplane fiberglass mechanics is likely correct,
they may just slobber it on nice and thick... If you can find one that
is building his own plane, that would be perfect... Other than that,
shop around for a homebuilder, bound to be one near you... Or give me a
jingle on the phone... None of this is hard once you have seen it
done...

Cheeers ... Denny