Having trouble shifting from first through third

Hi, quick question. Just had a new gearbox fitted to my astravan 1.9cdti sportive as other one blew up! Only done 55k!! M32 gearbox, not most reliable apparently?! Just got can back from vauxhalls had for few days now but find it quite hard to select 1st to 3rd and reverse. It's almost as if I have to force it! What could this be?? Also the clutch biting point now is v low literally half inch from the floor, do not no if they replaced clutch or not, was done as warranty job! Is clutch self adjusting or can it b adjusted? And wot is problems with selecting gears considering this just cost vauxhalls 3k!! Cheers