Great score, some people have all the luck.
I would dismantle the table saddle etc and give it a good clean. To clean up the top of the table you could use a scourer pad or steel wool, hopefully the table is not warped from the heat.
With the ballscrew I would remove it and clean it up with a soft wire wheel then inspect it for pits.
If it does need replacing, linear motion bearing on ebay are about the cheapest around and would probably cost around $300 fully machined and delivered from them.