Sorry Jan, I won't pick mine up until the end of this week, so I can't be too specific.
How many hrs on it?
Check blade rollers for grooves and bearings for slack/play.
Check the carriage rollers and carriage track for damage(bring a string & stretch it from one end of the track rail to the other looking for warpage)
Get the owner to actually cut a slab or two & check the cut for consistency & squareness.
On a good note, if anything is out of whack, parts are available from WM to fix it.
Go to the forestryforum (.com) & there are several WM LT15 owners that have posted info.
RD