You can easily bypass the evap, this might be relevant:
EVAP Hose Removal
I just did my second fuel pump replacement and its a bit of a job.
(did it 2x cuz I don't learn, not cuz it was necessary)
For me the big thing was figuring out how to support the vespa while not having it on the center stand. I did a combo of wheel chock / jack stands / use of hydraulic floor jack but the whole setup was a bit dodgy / unwise. Second time around maybe 2 hours start to finish. First time took better part of a day.
HTH