Hi,
just replaced a timing belt on td100 elx (well i had to, cyl head gasket went, so i thought i might as well).
There are marks on each of the main pulleys (Crank, Cam & injection pump).
There are also marks on the cambelt, which line up with those on the pulleys.
I didn't use any special tools. Needed 2 bolts to lock the injection pump into place (see the CD).
When replacing the new belt just line up the marks.
I was apprehensive, but fired up 1st time.
Good luck