P38 Manual Gearbox can't get Reverse

My 1998 2.5 DT won't easierly go in reverse as in it's very hard to find, also the gear stick in general feels very sloppy and all over the place when trying to put it in any other gear too. My car had a brand new gearbox fitted not long before i bought it. Can anyone please advise what may be wrong and where to start.. wondered it the stick and connection to the box may have come loose? Help!