Will the landing gear work mechanically in case of total power loss?
Not a real example, but this comes from the FAA, including some nice drawings around page 13-20:

The emergency extension system lowers the landing gear if  the main
power system fails. There are numerous ways in  which this is done
depending on the size and complexity of  the aircraft. Some aircraft
have an emergency release handle  in the flight deck that is connected
through a mechanical  linkage to the gear uplocks. When the handle is
operated, it  releases the uplocks and allows the gear to free-fall to
the  extended position under the force created by gravity acting  upon
the gear. Other aircraft use a non-mechanical back-up,  such as
pneumatic power, to unlatch the gear.
The popular small aircraft retraction system ..... uses a free-fall valve for emergency  gear extension. Activated from the flight deck,
when the  free-fall valve is opened, hydraulic fluid is allowed to
flow  from the gear-up side of the actuators to the gear-down side  of
the actuators, independent of the power pack. Pressure  holding the
gear up is relieved, and the gear extends due to  its weight. Air
moving past the gear aids in the extension  and helps push the gear
into the down-and-locked position.
Large and high performance aircraft
are equipped with  redundant hydraulic systems. This makes emergency
extension less common since a different source of hydraulic  power can
be selected if the gear does not function normally.
In some small aircraft, the design configuration makes  emergency
extension of the gear by gravity and air loads  alone impossible or
impractical. Force of some kind must  therefore be applied. Manual
extension systems, wherein  the pilot mechanically cranks the gear
into position, are  common. Consult the aircraft maintenance manual
for all  emergency landing gear extension system descriptions of
operation, performance standards, and emergency extension  tests as
required.