Check Engine Light on again. 2003 mini cooper 134,000 miles

2003 Mini had minor radiator fluid leak forever, but no mechanic was ever able
to find leak.  I could occasionally smell fluid but not all the time.  Had it towed
to garage when the temperature light went to HOT, tho there was fluid in
radiator.  I thought it had a head gasket blown issue.  Mechanic said all i
needed was to replace thermostat and casing.   Check Engine light has history
of flashing on sometimes while waiting at a light in low idle 1st gear, especially
if AC was on, but with acceleration it would go out.  Now it's on...again... and
won't go out.  Now the Green AC light on AC button has started flashing. Had
AC replaced 2 years ago. $$$
Do i need a new mechanic? Do i need a new car?  Since mechanic replaced
thermostat & casing It threw the following codes when check engine light came
back on:   P0128,   P2270
Haven't attached computer yet since AC light flashing started due to throwing
hands up in the air in complete and total despair and burrowing under the
covers.
From what I've said here, do you have any thoughts about what in the world is
going on here with my mini?  I am just shy of 70 years old. Have been driving
her for at least 15 years. It's the best Fountain of Youth ever!  Please throw
some hope my way.  xoxox