What's important is to make sure the strings have a proper coil around the pins. This helps stabilize the tuning. A sign of a good technician is how well the string coils are, and how uniform they look. (Guitarist: Make good tight coils without overlapping when installing new guitar strings, and the tuning will be more stable).
At this point, I'm only able to do the plain strings. The copper-wound bass strings had to be custom ordered, and they haven't arrived yet! Hopefully soon. Time is ticking!
I didn't want to risk breaking any hammer shanks because they seemed very brittle. So I installed new ones with the hammers. It's very typical to install new parts when the old ones might be good enough. The amount of labor involved with dealing with old parts usually can exceed the cost of just buying new ones. Just installing new parts can sometimes be cheaper overall.