To this, I'd add - be prepared to pay for this.  Most places will pull
prints from slides without making an internegative, and the quality
for cheap slide prints is spotty at best.  A good lab will scan the
slide at high res, correct frame to frame per the scan histograms, and
print with a calibrated system.  Old-school labs will wet-process
internegatives and print optically to color paper, though places that
do this are few and far between.

I've had bargain-basement slide prints made for people before, and the
results were horrible - I could have done better with 10 minutes worth
of work with my film scanner and inkjet.

The biggest crime that most places commit when printing from slides is
to mishandle exposure and exposure comp.  I've seen more dark, muddy
prints from properly exposed slides than I'd ever thought I would.

Yes,  Invest in a film scanners.  And a good photo printer.  It is truley
amazing how well you can print your own photos when you use the right paper,
ink etc...  If you are only interested in doing small prints your investmant
will not be allot.  If you want to print large the spend the money on a good
scanner to start.