Unless I was pretty big/heavy and traversing rough roads at speed fairly often, I would just continue to ride the Maruishi the way it is. It's not going to cause any kind of sudden failure imo, and might serve well for many years, which is plenty long enough to stumble upon another opportunistic purchase.

I would double-check the headset smoothness first though, after removing the stem and front wheel and installing a stem with no bars to simulate the steerer-shortening effect of having the quill expanded in there.

I suspect the headset could now use at least some readjustment, based on my experience with many used bikes.

A headset even slightly tight will have worse of an effect on handling than the slight geometry change, and quickened steering with shortened front-center would be an improvement on perhaps half of the bike out there imo, at least on those that are fitted as a road bike is intended, as here with stock stem length.

I've bought a lot of used bikes and have found hidden defects on most of them, most often defects with the rear wheel, rim cracks or the case of a very-bent rim having been pulled back into true by way of radically-variable spoke tensioning, which can mean quite a lot of work and cost to correct if a similar rim is to be sourced and the wheel re-laced.
I found a very clean old '86 Sirrus last weekend at an annual community benefit flea market up in Foresthill, went to tune it up yesterday but found the rear spoke tensions all amiss when I tried doing a little truing and tensioning. An hour later the wheel was usable, but still with a couple of flat-spots. Thankfully the bike only cost me $25.