You need to rebuild the steering rack. If that is not something that you are able or want to tackle on your own, you will need to replace it with a rebuilt one. Those are a few hundred bucks, so not bad, or you could try your luck with a used one. It's not a difficult job -- the only tricky part if you haven't done it before is popping the balljoints on the outer tie rod ends, but you can rent a tool that makes that job easy. The rest is a snap, just 2 U-bolts that hold the rack to the crossmember, then the 2 power steering hose banjo connectins (one large bolt each), and you're out. If you have a balljoint tool the whole job will take you 20 minutes, including jacking the car up. You will have to get it aligned after you put the new rack in.
Rebuilding the rack yourself is not a huge deal -- they are pretty simple inside if you are able to find the rebuild parts, seals, etc -- but it means more downtime for the car because after you get the rack out, you have to leave the car taken apart while you redo the rack. If you have a rebuilt or good used rack already on hand when you remove the old leaky one, then you can have the car back on the road and all fixed in just an hour or two.
You're already more than halfway to 500k. Why not set a higher goal than that?
If you take care of it (change the timing belt on schedule, use synthetic oil, take it slow when the engine is cold, and don't overheat it), it will probably last to a million.
