Leave it alone. It’s an old car. Don’t go looking for or creating problems where they don’t exist.
Does it have a reservoir for the PS fluid? I’d just buy a dollar store turkey baster and suck out as much fluid as possible and refill with fresh stuff (the exact fluid required/ recommended by manufacturer specification).
Repeat this process every few weeks for a while. The fluid should start to look noticeably cleaner. Then leave it alone except for monitoring and maintaining fluid level.
You’re fortunate that the paint is in nice shape. I’m sure you already do, but just keep putting some good wax on it a couple of times per year.
Buy your car a treat of some kind. Surprise it! Enjoy the ride! Then find a new hobby or activity.