I've never tried to blow the seal out after seeing one blow fluid around the shop, making a mess, but of course you'd prob contain the area with a baggie.
I often use the "woodscrew" method, cuz once you get the seal out, you can see that the screw butts into the huge cast iron boss in the case, no-where close to the "shaft" unless you aim the screws 45* towards the shaft (thats in the middle). ( I accidentally discovered the screw-thread thing, cuz I was screwing in the slide-hammer screw, went too far, and with the screw butted inside against the case, - the rotation of the thread pulled the seal out. )
The old seal will be stiff with age, and less inclined to move with any shaft/bushing wear, thus leak, - but the new, supple/soft seal will be inclined to move a little allowing the seal to conform to some shaft movement.
Good luck .