1994 Other Peugeot Models car is failing to start

Engine Mechanical problem
1994 Other Peugeot Models 4 cyl Front Wheel Drive Manual

hi there my car if failing to start its ticking over but isnt kicking in, when I bought the car I got told the timing belt mite need changed could it be that?
if it is the timing belt are they easy to change with the enigne in place or would it be easyier with the engine out? And how would I be able to get hold of a timing diagram for it?