The LN engineering IMS bearing kit is $650. Additional labor is minor if your transmission is already out (RMS, clutch). $2,500-$3,000 should cover the IMS bearing
including with a full clutch replacement!
If you don't need a clutch replacement, you can go for the Guardian Jr. for $250 which will give you early detection of IMS bearing failure. If your car is a tip, or you don't need a clutch, or your car is a 2005+, the Guardian Jr. seems like an inexpensive way to help relieve the massive IMSB paranoia.
To me, the following strategy seems pretty sound:
- Install a $250 guardian Jr.
- Enjoy the car. Use good oil. Change it every 5,000 miles.
- If your transmission is down for a clutch, RMS repair or any other reason, go ahead and spend the extra ~$700 and install an LN IMSB.
- If your Guardian Jr. gives you an alert, install an LN IMSB.
I don't understand the never-ending M96 gloom and doom... The failure rate isn't that high. It's more an issue if you don't catch the failure in the early stages (bearing seal and bearing race start to deteriorate), you can do severe engine damage (ball bearings rattling around your engine). The Guardian won't prevent the failure, but supposedly is very effective in early detection, preventing the severe engine damage which is really the big issue...