It's under the intake manifold, on top of the engine.
You have to remove the manifold.
Not a difficult job, but does take some time
See answer to location of manifold question
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The starter relay is inside the starter. You will need to replace the starter.
it can cost any were from 200 to 450 to replace the starter.
Remove the positive cable from your 1997 Oldsmobile battery. Remove the starter cables from the front of the starter. Remove the starter retaining bolts. Reverse the process to install the new starter.
I had to replace a starter in my 96 and it cost around $350.00
There are some detailed articles on changing starter motors at ; http://www.carbasics.co.uk
the starter is located under the intake manifold The large power cable on the battery most always goes to the starter which is on the bottom of the engine near the transmission area and is most likely below the intake manifold.