08 vivaro 1:9 very hard to put into gears ?

I wouldn`t think your fault has anything to do with the work done on other items you have mentioned,you don`t say if it goes into gear easily with the engine off but if it does then suspect clutch clearance problems. Check under g/box bell housing for signs of fluid/leaks,if there are any then suspect slave cylinder,then it may just be a worn clutch,if any of these then it is a g/box out job,book time about 7 hrs,also try giving the clutch a bleed and make sure your master cyl. is well topped up,good luck.

cdc
May 2014