Many 97 and 98 Qs are eligible for free alternator replacement under a voluntary recall that's described in a Service Bulletin, provided that it hasn't already been done.
I emailed Infiniti with the VIN on my car, asked about the replacement campaign and got the following reply a few months ago
[email protected] to me show details Jun 10
File # 6516xxxVIN # JNKBY31A9WM 5015xxx
Dear xxxx,
Thank you for contacting Nissan North America, Inc. and allowing us the opportunity to assist you.
Please be advised that a review of our records indicates that the vehicle with the vehicle serial number listed above is involved in the open recall as follows:
OPEN R2009 Q45/I30 ALTERNATOR ITB02-043
Please contact your local Nissan dealership for an appointment to have the necessary repairs performed on your vehicle. These repairs are free of charge to you.
Thank you for giving us the opportunity to be of service.
Sincerely,
Nissan North America, Inc.
=-=-=-=-=-=-=-=
You might call your dealer, too, and be sure to give them the bulletin number in the email I got. Good luck!