Does it fit your needs?
Look in the exhaust ports and inside crankcase for signs of its true condition as well as how easily it will start and perform under full loads. The ST2 is a solid performer, but the Kohler portion is obsolete and in many cases unserviceable if anything goes wrong with it. Check to see if the engine is equipped with ring gear on the flywheel. If it lacks that, then a later conversion out of the Kohler setup will be more complex and costly. Kohler did not use SAE housings and adapters but rather opted for customized hardware - this makes changing generating hardware a bit of an extra hassle.
That unit should pull 8kW.
$2250 is certainly within reason for a good condition fully operational setup. Ask yourself if it is within your own budget and needs.
dieselgman