Gearbox controller

Hello everyone
I have caterpillar 12h grader have problem with gearbox so after I check it I discovered that the ecu is faulty then I decided to make controller for it using relays and diode and it worked perfectly.
But I think if I us arduino it will be better
I'm not too much good in programming I write one programme but didn't work so I need help .
The input signal is :

  • Nutral
  • Drive
  • Revers
  • gear one
    -gear two
    -gear three
    The output signal :
    Selonoid A
    Selonoid b
    Selonoid c
    Selonoid e
    Selonoid f
    Selonoid g
    Selonoid h
    In this order:
    Drive one= selonoid a and f and h will work together
    Drive two = selonoid c and e and h
    Drive three= selonoid c and g and h
    Revers one = selonoid a and f and h
    Reverse two = selonoid a and e and h
    Revers three = selonoid a and g and h
    Nutral = all the selonoid off.

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Given your selector provides a 1-of-N connections to the (+12? ) supply, your diodes/relays

solution seems very sensible - how would an arduino help?