i would not count on your face shrinking.

hmm,...

what he's saying is ok.  it's true another cavity could appear because
it's so difficult to brush back there.  sometimes i tell patients to
use a children's tooth brush because it has a smaller head to get back
there.  but let me answer some of your other questions.

there is no reason to keep a wisdom tooth, usually.  most people can
do without them and most people don't even use them to chew.

there are always possible complications to surgery of any kind.  an
upper wisdom tooth could have what's called a sinus perforation (a
hole between your sinus and your mouth).  no major nerves are in the
area, sometimes adjacent teeth can be damaged.  some swelling and pain
is normal.  however, upper wisdom teeth are usually really easy to
take out and very little pain afterwards.  of the hundreds of cases
i've done, upper molars only only a handful had angonizing pain.  the
truth be told is no one can really predict how your body will react to
trauma.  but removing an upper wisdom tooth is usually very easy, and
very A-traumatic.

i don't think your facial proportions will change at all.  you will
possible swell, but after it's all done you should be good to go.

Good luck...

C