I've been nearly 6 years in Monastir. So I know a little the country.
Safety is very good. Marina Monastir is camera guarded. Nice and friendly marineros.
Since my Sharki is a lot smaller than your boat, so I always haul out at the shipyard in the marina.
They (at the shipyard as well as other shops) have done all work very good and very cheap (less than half the price as in Europe).
It might be difficult to get special spare parts. Things I didn't got in Tunisia have been shipped from www.svb.de (Germany) within max a week to Monastir however.
Living cost and marina fees are very low as well as Diesel fuel. Here in Greece now I pay 3-times more.
Amel Sharki #60
Currently Kalamata, Greece