Given the age of the system in question, I'm thinking the lifespan of the current one is reasonable. In fact, the current one hasn't completely failed yet as I'm looking to replace it as part of diagnosing another problem I'm thinking is related to the power supply.
If it's a matter of this power supply starting to go bad, replacing it with another (effectively an OEM one) should restore its operation to normal levels. I believe this system is at least 3-4 yrs old (probably leaning more toward 4 yrs if not older than that) and is in an extremely dusted environment.
So, we'll see how it goes. Plus, going with a replacement of the one that's in there now (same make/model) ensures it will fit and the cabling won't bump into other components, etc.
We'll see how it goes.
Peace...