The struts for a 97 PA and 97 Riviera are the same, and they are 62.79 each at rockauto. KYB 334677. Yes, you use them with your current springs and mounting hardware. You'll need a spring compressor and an impact wrench.
Buyer's Guide : KYB 334677 Strut
BUICK PARK AVENUE 1997
BUICK RIVIERA 1997
OLDSMOBILE AURORA 1997
Please refer to catalog for application details.
98 Riviera SC3800 All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54