Gear oil leak in front and gear shift lever loose

Once the freeplay is set it should not alter, the driven plate linings may have come loose or the pressure plate may have a broken spring. If so replace as a kit including the throw out bearing and spigot hearing.

check the oil level in the transmission as there may be insufficient / too much oil for correct operation of the transmission . There may also be a leak in a line or plug that was not tightened properly

sounds like a vacuum leak, older vehicles used vacuum 2 shift gears, the biggest leak you could have would be the EGR valve and any vacuum leak could cause the engine 2 die

This information is from my genuine service manual. I hope it is of help.
Non-turbo
Turbo
Sedan Wagon
Type 5-forward speeds with synchromesh and 1-reverse
Transmission gear ratio
1st 3.454 3.454
2nd 2.062 1.947
3rd 1.448 1.366
4th 1.088 0.972
5th 0.780 0.738
Reverse 3.333
Front reduction gear Final
Type of gear Hypoid
Gear ratio 4.111 3.900
Rear reduction gear
Transfer
Type of gear Helical
Gear ratio 1.000 1.100
Final
Type of gear Hypoid
Gear ratio 4.111 3.900 3.545
Front differential Type and number of gear Straight bevel gear (Bevel pinion: 2, Bevel gear: 2)
Center differential Type and number of gear
Straight bevel gear
(Bevel pinion: 2, Bevel gear: 2 and viscous coupling)
Transmission gear oil GL-5
Transmission gear oil capacity 3.5 2 (3.7 US qt, 3.1 Imp qt)

2000 TOYOTA TACOMA 2.7L 4-cyl Engine Code 3RZ-FE

Engine Oil Grade 1......API* All TEMPS......5W-30 Optional ..10W-30
Engine, 2WD, with filter..........5.5 liters
Engine, 4WD, with filter..........5.4 liters

Manual Transmission,......GL-5/ GL-4 All TEMPS......75W-90
Automatic Transmission,A340E......AF3 / A43D......AF3

Differential, Front/ Rear W/ ADRD......GL-5 ALL TEMPS......75W-90
Differential, Front Less ADRD......GL-5 ALL TEMPS......80W-90

Transfer Case,......GL-4/GL-5 ALL TEMPS......75W-90 Gear oil.

Capacity:
Cooling System, Initial Fill..........8.5 liters
Automatic Transmission, A340E Initial Fill..........1.6 liters
Automatic Transmission, A340F Initial Fill..........2 liters
Automatic Transmission, A43D Initial Fill..........2.4 liters
Automatic Transmission, Total Fill
4 speed A340E..........7.2 liters
4 speed A340F..........10.1 liters
4 speed A43D..........6.5 liters
Manual Transmission, ..........2.5 liters
Differential, With ADRD Front..........1.2 liters
Differential, Without ADRD Front..........1.1 liters
Differential, 2WD V6 Rear..........2.6 liters
Differential, 4WD Extra Long Rear..........2.5 liters
Differential, Short WB With LSD Rear..........2.7 liters
Differential, Short WB Without LS Rear..........2.6 liters
Transfer Case, Electronic..........1.2 liters
Transfer Case, STD..........1 liters

is yours carb,if not 23- manifold air temperature (mat) sensor or circuit (1990 and earlier models) 23- intake air temperature (iat) sensor circuit (fuel-injected models) if its carb,,,,,23- mixture control (m/c) solenoid or circuit (carbureted models)

CHECK SHIFT LINKAGES FOR LOOSENESS BINDING AND WEAR.ALSO LACK OF LUBRICANT.

Where are you seeing the oil leaking from? Remember that gravity will cause the oil to drop down. The wind will also cause the oil to blow back while you drive. Look for the forward most and top most areas that are covered with oil. Common leak areas are the front oil seal (oil will look like it's coming from the bell-housing. Another common leak is the shifter plate gasket, just below the shift lever. Oil will be found draining from this area. I have also seen shoddy mechanics use the wrong bolts to hold the rear housing onto the main housing of the transmission. If the bolts used are to short, oil will leak between the main housing and the tail-shaft housing. Charlie

possible range selection detent switch not working causing to get stuck some times in one range only and wont shift to other range 4wd light in dash just keeps flashing for about 10 seconds then goes to previous state this then can jam up 2wd 4wd lever that you then cannot move.
there are 3 switches 2 on trans/transferr case, 1 on front LH diff axle tube actuator (shift on fly). can cause damge to the electric actuator then on transferr case.
suggest you get a dealer to look at or some one that knows this system. is also vaccum operated on front diff shift on fly unit and there were 2 different systems fitted to these vehicles push button 4wd on dash and lever next to gear lever which i take is yours

Internal engine wear, leaking piston rings, seals, gaskets etc. Time for an engine over-haul.