Mike Halls' engine from Pelican posted above appears to be a great deal, I ve sold quite a few engines
in the past presently just don't really have an extra in that price range..
I do have a '91 turbo but it's low mile and i'm reluctant to sell unless all the money is on the table,it
sounds as though the only useable items on your engine may be the injection and some odds and ends
these engines tend to do a lot of damage when something comes loose.
Your mechanic was right for the most part for what its worth a good replacement engine could likely be
found far quicker,and cheaper than the requisite rebuild to yours which in the long run may not be
prudent.
There are usually tons of good reasonable 964 engines milling around under 6k you just need to wait
for one when your finances are in shape.
In the mean time get a replacement cooler or have yours cleaned and have your oil lines removed and
thouroughly cleaned...Bert