Toyota Repair: 1991 Toyota truck, fuel mileage, gas mileage

Question
I have a 1991 Toyota truck, base model 2WD with 22RE, 5sp, etc.  The truck has 262,000 miles on it.  Two problems:
1.  When I shift gears, frequently the shifter pops into neutral.  Seems to be just about any gear.  IF I wiggle side-side while pushing toward the direction of that gear, it will stay, as the shifter moves more fully into that gear.  I took the shifter out this weekend and changed the plastic bushing, but the old one was in GC.
2.  My gas mileage seems to be falling.  This past summer it was around 29-30 MPG, but this winter it's at 23-25.
What do you recommend?  I drive about 70 miles/day 5days/wk.

Answer
There are two bushings for the shifter, one at the end of the shifter and one in the shift tower, this one is about 1+1/2" in diameter, if it wasn't replaced doing so will fix the shifting problem. Can't help with the fuel mileage there are just too many things that can affect mileage, including driving conditions.