I bloody love our Yaris; comfy, reliable, great visibility and if you stay in gear and change quickly they’re almost fast to 60.
Get under it with some underbody wax. Most parts, like bearings, can be replaced easily with scrap items from a donor car. Looks like this one has got a lot of salt on it. Give it a good wash underneath, inspect, undercoat and repair and you’ll be grand.
OEM Denso plugs (very cheap), air/oil filter and new semi syn (consult the manual carefully, the oil spec/temp chart is backwards as hell) and the motor will sing.