The new bearing slid in like it was made for it. I think it was the corrosion on the outside of the old brass bearing shell that kept it from sliding out (plus the screws). Not sure the material of the stern tube, perhaps monel, but once that was cleaned up, the new bearing went in easy. At most, a block of wood and a hammer.
Don't make too much of this job - it's not a big deal. If you don't have a reciprocating saw, it's a good excuse to buy one.