Newbie - advice re repairs to old Thomas Trackmaster trains

Well - I can’t rule out a bit if corrosion - we had left batteries in some (stupid I know) but have sanded off any obvious corrosion as wasn’t too bad… the trains did work before (say about 6 years ago…). Thanks. Sounds like it might be a job too far for us. 🫣. Is there a home for broken ones (as spares?)