location of alternator and how to replace it

if you have a 4.9L engine the starter is externally mounted and not much trouble to replace. Since you're asking this question, I suspect you have a 4.6L engine. In that motor, the starter is mounted internally under the intake manifold. Not an easy starter to do, even for an experienced machanic.. Here's a directory link for you: http://repairpal.com/cadillac-repair-in-tacoma-washington