The Linn bearing has a very tight tolerance. When used with the recommended Linn black oil, the spindle should slowly float down within the bearing well, sometimes taking minutes to settle. If it drops too quickly, the tolerance may be off. With respect to wear on the point that comes in contact with the thrust plate, spin the platter ( without the drive belt), the platter should spin freely for a prolong period of time. Also, you can purchase an inexpensive stethoscope and listen for bearing noise, but you need to know what to listen for as you currently have no reference point.
Yes, it is difficult to find a nos bearing and that is due to the fact that the bearing and platter were sold as a set. A lot of people have upgraded to the Cirkus bearing, therefore, there should be a lot of used but excellent condition old bearing/platter combo that can be purchased for an excellent price.