While no particular expert on the Minarelli V1, in my experience sprocket replacement is usually a quick and nearly painless process, usually not needing special tools.
As with flywheel removal, there are workarounds in the case where special tools would be helpful, but are unavailable.
Depending on how it's mounted, the difficulty of changing a front sprocket versus a rear is about the same, and either one can be done quickly if you know what yer doing.
(That means it'll likely take a rookie a while......)
Generally changing the front sprocket by one tooth, is equal to changing the rear sprocket by four teeth, so it depends on how much of a change you wish to make, if minor, do the rear sprocket, if major, do the front.
I hope that helps out a bit, and yer welcome to try referencing Tomos sprocket change info (posted under "tomos boatload") to get a general idea of the process.