could easily be input gear mainshaft spline wear you can check by removing pto cover off rear of transfer box,as well as ujs ,diff brgs etc ,checking state of oil can help sometimes as to condition of unit
Then my my old son you are fooked find a m8 that is good or you may find that 300's get expensive after a few garage bills
However check the prop shaft uj's first if they look dry grease them any play in the uj's can cause that how old is ur landy and what miles has it done
fokin hell... for someone looking for help your posts are short and sweet....
you could give a bit more info, but seeing as you already said your skills are basic, just take it to a garage as clearly you won't be checking whatever people tell you here to check