Given ~6 years of aging, on what was a PSU built for an OEM system (so built to a pricepoint, with Caps, Fan etc likely being relatively 'cheaped out' on and only warranted for the 12? months provided for the system as a whole), wouldn't fill me with too much confidence, unfortunately.
I'd still put it borderline. May well be fine, might not. Only way to know 100% would be to test it out and see.
As I mentioned, the FSP unit should have sufficient protection - They're still a reputable OEM. It's better than some off-brand junk, even brand new, that's for sure. Try it out. If you have unexpected crashes/instability, it may well no longer be up for the task.
*FWIW, I'm not sure whetehr Lenovo use proprietary connectors to the motherboard. If they use an ATX standard 4or8pin EPS and a 24pin, a PSU replacement is easy enough.