I have seen many references in this discussion room to GM's intake
manifold or gasket sealing failure ohe 60 degree engines.

 My 81 year old mother has a '93 Gran Prix with a 3.1,  which I've
posted about in here before.   As you might guess, at her age she isn't
inclined to trade her car in favour of a newer model.  She just wants to
keep what she's used to from here on out.

 The car has performed remarkaly well in terms of never needing any
repairs, for about 11 years.  However, it recently needed $1400 put into
the transmission, and about a year ago another $700 for some new
injectors and an ignition module, IIRC.

 The car has about 130K miles and so I can't kick too much about the
transmission needing overhauled (a drum inside it developed a problem,
IIRC, and they just did a complete rebuild).

 But I generally wouldn't expect a similar catatrophic failure with the
engine, since it's common for most of them last to 200,000 miles and
beyond.  Hence, I would normally consider keeping this car since the
transmission has been redone and meanwhile the engine should still have
a lot of life in it -- EXCEPT for the fact that this is an engine design
with some kind of inherent sealing problem.
 
 Also, I have noticed a vague smell of anti-freeze several times when I
enter her garage after she's een driving it, but see nothing visibly
wrong under the hood (so far).

1.  What specifically is the sealing problem?

2.  What engines, years?

3.  Are there preventative repairs to be made before hand?

4.  What is the typical result of the failure resulting from the
manifold sealing design flaw?

5.  Any tell-tale signs that's about to happen?
TIA