Your Kubota Grand L is equipped with the Inteli-Panel, and upgraded version of the original Inteli-Panel found on the L-1 Series Kubota's that preceeded your L3130.
The light is on to tell you that a "Service" is required.
The "wrench" light is part of the Service Reminder Programming uploaded onto the Inteli-Panels chip set.
Kubota programmed the maintenance intervals and Service Requirements into the Inteli-Panel with the instruction to illuminate the "Service Reminder" lamp at specific "hour" intervals.
Depending on the approximate hours displayed on your hour meter, it will tell you which service job is required.
Since this tractor is new to you, you're probably going to want to change all fluids, all filters, and service the cooling system, as you have no way to know wether or not the preceeding service reminders were in fact adhered to.
The Service Reminder and Wrench Light can be re-set by the operator (instructions are on page 42 of the owners manual) after preforming the service job, as follows:
-make sure the engine is running and the dash display is indicating the "hour mode"
-hold down the "display" and "travel speed" buttons at the same time for a few seconds
-the lamp should go out
That'll get ya goin!