Transit 2001 Gearbox problem?

To start off, the gearbox seized while driving. 1st and second eventually went and 3rd and 4rth were not there either. got a mechanic to come to sort it, after much pushing and pulling the gears became free. The only problem now is, there is no neutral, its constantly in gear. Can anyone tell me what is wrong and if its easy to fix. As the mechanic done a runner on me. :(
Would really appreciate any replies.

The van is a 2.0 litre swb fwd 2001 if this helps.