I would test the oil pressure switch, electrical and oil system with a mechanical guage before tackling a major. More than likely an electrical gremlin or stuck sensor after sitting for so long.
That being said, they're not horrible to change. Just a bit in depth and time consuming. Case & New Holland are essentially the same machine with some mechanical & aesthetic differences. Do some research into whether you are mechanically capable of the endeavor before digging in.
The case new holland parts store (
https://www.mycnhistore.com/) should help a bit. Your machine is basically a case 445 series 3 or case 450 series 3 with the same 445T/M3 engine.
Find schematics, manuals, specifications and diagrams for PUMP, ENGINE OIL & RELATED PARTS (87380450). Find genuine OEM parts for your needs.
www.mycnhistore.com