i am unable to select a gear?

Clutch fluid won't have anything to do with being able to change gears - unless you can't operate the clutch - to disengage the engine from the gearbox.
Clutch master cylinder is located on the front bulkhead. Open the hinged panel under the front windscreen - a big coin will open the quarter turn fastener on each bottom corner.
It is on the drivers side to the right (as you face the cab) of the foot control valve. A small translucent plastic chamber with a screw on cap.
To tilt the cab:
(1) Find the cab release tool -a steel key with a triangular shaped handle. This is probably thrown loose somewhere in the cab - under the seat or in the glovebox - I think originally there may have been a plastic clip for this on the floor pan just under the drivers seat. Or possibly it's lost!
(2) Go to rear of cab on drivers side. There is horizontal lever with a round black knob. PUSH this inwards (towards the passenger side) and insert the big key into the cab lock release (orange plastic socket) and turn and then PULL key outwards.
Torsional spring on cab will raise it partially. You then have to lift it manually the rest of the way (and it is heavy). Be ready to engage cab support stay (mounted on drivers side chassis rail) with free hand.
Note:
Good idea to make sure before you tip the cab that:
(1) there is nothing heavy sitting on the seats as (a)this will make it harder to tilt and (b) the same object might go through the windscreen!
(2) cab doors are closed and mirrors are folded in against cab sides.
(3) There is enough room in front of and above the truck for the cab to tilt forward (and upwards remember!) - without hitting off anything.

JD
April 2008