It probably has fried capacitors from that era. You have a few options.
Rebuild it yourself by using YouTube videos about old capacitors.
Send it out to a rebuilder. It will cost $300-$500.
Look for one on eBay.
You're going to be hard-pressed to find any troubleshooting guides on your TVSS. I know. I went down this rabbit hole DEEP a few months ago when adding keyless entry to my truck. I even bought the TVSS full guide off eBay.
In the end, I decided to install an RS3200 system instead...