I had never heard of a Gilera 106, much less a 106cc, as the typical engine sizes in Italy have always been 50cc and 125.
There have been a few, rare 90cc, but that was it.
Agewise, the categories were 50cc for 14y.o., 125 for 16y.o., 150/175cc for 18+y.o. riders.
As 106... meaning 10.6cu.in does mean 175ccs, that is a true possibility.
You might find bits for the bike on the European scene; your best bet is
www.ebay.co.uk, lots of parts there and it's in English.
Pity many sellers will refuse to ship to the US (but if you have payPal...
) often as retaliation that US sellers will not ship to Europe.
Gearbox is most probably a 4-speed, on the right, 1st up, 2-3-4 down.
Brake pedal on the left.
Definitely an easy bike to work on, 6V DC generator/magneto will make feeble light for night driving, but hey! You still get 70+mpg !
AND points/condenser ignition means you can retard the spark and run on the foulest regular ever, and she'll still get the job done.
AND no battery to worry about, either...
Consider her a project-after-next. Could require more hours than dimes, but will still be a talking piece when it's over.
OR
Sell it to the first pimply youth who is willing to ride "the only vintage Italian bike this side of the Mississippi!"