I'm a new Audi owner and I've been told that once you change your spark plugs the computer should be reset. Is this true?

I bought all my Timing/Trans service parts from Autohaus Arizona which was a site recommended from Audipages. Going to use the Audi Trans fluid (G052162A2) with that service, I bought it from ETYPARTS @ 12.00 a bottle, pretty expensive stuff but this is what several other A8 owners recommended.

I have a 1997 A8 Quattro 4.2L
Convenience Pkg
Cold Weather Pkg
Warm Weather Pkg

You would be resetting the major service interval back to "zero." Typically set to trigger every 2 years or 30K miles, though you would have to look it up for your car. If your car has the center multifunction display like the C5's did, it probably puts up the "Service in x miles" warning on the display. On C5's it can be reset via the instrument panel. See the owners manual.