Tailgate Lock Not Working Properly

the tailgate lock on my 94 disco has given up, ive had it in bits and re fitted but cant find where to put the spring that aparently is prone to snapping, the door will only lock and unlock and open from inside, ive consulted the old haynes manual but does not really show me clearly what ime doing, i am practically and mechanically minded but can anyone tell me is this a diy job or one for the profesional money grabbers.

Not to bad to fit but be very paitent

Yet another one of the 1001 things I have had to do to mine. Soon be a bloody new one