Yes, to change the seal on the crankshaft lower bearing from a lip seal to the carbon seal you must change the lower crankshaft bearing. To change that bearing you are going to have to open the crankcase halves. Then you will also be able to change the oring that goes around the lower bearing outer diameter. Look also on Ebay for the parts. Sometimes you can get a deal especially for the lower crankshaft bearing which is expensive.
While the crankcase is open it is easy to install a new lip seal on the top crankshaft bearing. I would do that too for sure. Notice that there is NO oring around the top crankshaft bearing. If you put one in it will block the top bearing drain.
Here is a photo of a 1956 Javelin that might help. Notice the oring around the lower crankshaft bearing and that the upper crankshaft bearing does not have an oring. The dark band at the upper end of the upper crankshaft bearing is the lip seal. It slips onto a step at the end of the bearing. It is easy to drive the seal off and then press a new one on.
