Yes, the front bolster will have to come off.
So will the pulley and the front cover on the engine. The seal is actually in the cover and it seals against the hub of the pulley.
Removing the pulley can be tricky, search on here for several methods of pulling it off without breaking it. A, B, BN, Super A, C, & Super C all have the same kind of pulley on the front of the crankshaft.