In my area - SF Bay, the price to replace the IMSB is about $1800 ($1000 labor and $800 parts and supplies). If you add a new clutch ($500) and new flywheel ($700) to the job, the price is in the low $3000.
If you do decide to replace the IMSB, then look at the thread below. The general recommendation seems to be to install the IMSB without the outer seal so 'splash' oil lubricates the bearings. I take it that this advice applies whether you install a stock, Pelican Parts or LN Engineering bearing. The LN Engineering ceramic bearing is the best choice for longevity.
http://986forum.com/forums/general-discussions/43117-excellence-say-just-remove-ims-outer-seal.html