Can you replace a battery on a 1997 Jetta without messing up computer and causing it not to start?

Yes Of Course. When Replacing Any Battery Remove The Negative Cable First, Then The Positive. Then Installing The New Battery Install The Positive Cable First Then The Negative. Dear reader; Many computer equiped autos have no protection against damage if the battery is installed backwards. Some have fuses in critical circuits which offer some protection. Jump starting can also cause these fuses to fail. Dwight