Remove hotshoe adaptor, then remove 4 screws as in pic below, lift out the cover plate then loosely refit the 2 screws of the back moulding, this will prevent 2 plates falling out when you eventually get it apart.
Remove 3 screws in top moulding as shown in next 2 pics
The top moulding is now held on with 2 plastic clips which are part of the moulding, if you try to lever the top off then you have a very good chance of breaking them.
The easiest way is to carefully drill 2 small holes (about 1.5 mm) in the casing, making sure that you only go through the casing and do not drill the plastic clip inside,
you can then insert a small screwdriver and carefully push on the clip while you prise the top off, it helps if you've got 3 hands !
Position of holes in pics below:
Once the top is open then you will find another 4 screws which again fix into 2 plates so follow the same practice as you carried out on the base.
After that the bottom section will come apart.
DO NOT ASSUME THE MAIN CAPACITOR IS DISCHARGED JUST BECAUSE THE FLASH ISN'T FIRING, DISCHARGE IT CAREFULLY, IT CAN GIVE YOU A VERY NASTY & POSSIBLY LETHAL SHOCK.
The fault you describe may not be the main capacitor faulty, it sounds more like the large yellow 3.9uF is shorted. (A common fault, this can be replaced with a similar but more common 4uF type)
Good Luck, and let us know how you get on.
Ray