I choose AutoXray 5000 and 6000 scan tools 20 some odd years ago for use on the Buick as GM OBD-1 as well as any future car I might have with OBD-2 protocol.
I could not see investing in a scan tool for just the Buick and then another tool to do the same thing for any other vehicle I would own.
While the AutoXray products were discontinued around 2007 when the company was acquired, I still find it an awesome tool and recommend it to anyone who asks.
Spec sheet for the 6000 model is attached as well as the owner's manual. these can be purchased via ebay for around $130 or less nowadays. there are plenty of 6000 models listed - just checked. Around 2003, the 5000 model was $400 retail and the 6000 model was $500 retail. Then you could pay another $100 for a unique code to enter on the tool to unlock the full gambit of OBD-2 parameters - for each vehicle manufacturer's enhanced parameter listing. Can't do that today with the tool no longer supported. see manual for listing of generic vs enhanced OBD-2 parameter listings. Just confirm tool condition and how many of the interface cables remain with the tool. Seller might know or disclose what enhanced parameter sets are available.
The 6000 model also has a data logger of sorts built in. it will record 14 snapshots of data (20 parameters) before and after the record point for a total of 29 snapshots of data. Sample rate can be set to .5 seconds to 5 second interval between snapshots recorded. And the data can be exported to a laptop. One of the key points to keeping old laptops and desktops for serial port and XP or XP emulation.
Attached is a pdf of the spreadsheet I made years ago for logging the OBD-1 parameters from the 87 ECM. What you find for the '98 Riv will probably be similar. All the available OBD-1 parameters will show up on the tool. there was no enhanced mode for OBD-1 like there was for OBD-2.
And the tool can also serve as a battery conductance meter with the addition of the EZ-Charge 200 module made by Midtronics. With this combination, you have the similar capability that Advance Auto Parts has with their Midtronics 1200 battery diagnostics tool minus the on-board printer. EZ-Charge 200 is also on ebay.