wmorrow
I've seen Steve at VAS change his beloved Uni-Pivot arms on his VPI. It seems easy, until ....
change arm: pull out mini-din connector from the VPI junction box: that mini-din connector now dangling from delicate tonearm wires. Simply lift arm up, put down in safe location.
Pick up spare arm from safe location, with alternate cartridge pre-mounted, pre-aligned. Place on the arm base spike, plug in it's mini-din connector.
NOW, cartridge body height might be different, reset VTA as you mentioned. Cartridge weight likely different, it's recommended tracking force probably different, and thus anti-skate should be re-adjusted.
VPI arms used to skip anti-skate, they said "put a twist in the wire" from tonearm to junction box (oh that's precise), then they started making aftermarket anti-skate devices, VPI now offers them
I have changed arms on my friend's Technics B500 base, no delicate wires involved.
Changing a headshell with pre-aligned cartridge, then the same VTA/Tracking Force/Anti-Skate is needed.
Second or 3rd arms, very carefully aligned, ready to go is much preferred if alternate cartridges are used.
A true Mono cartridge DOES make a difference, slight or a lot, varies