I assume you're talking about the hardware to mount the opener to the ceiling of the garage? If you are, I REALLY like the angle iron that has the pre-punched holes in it as it allows a load of flexibility. It's readily available from all the big box stores near their openers. The hardware to mount the opener to the door should be included with the opener.
For one door you'll need 1 - 8' stick, several 1" bolts, nuts washers, lock washers to fit the holes in the iron, I "think" the last ones I used were 5/16". 2" lag screws the same size with washers to screw the angle iron to the ceiling. The HARD part here will be with out knowing which way your ceiling joist run, we can't tell you how to cut and piece this together.
When you install the opener...make sure your springs are set correctly, meaning your door should lift with one hand, and stay where you leave it on the track, in other words balanced. If you have torsion springs be OMG freakn' careful...if you don't know what you're doing and are fully aware of the hazards associated with them...don't touch them...they can be killers.
As for the stiffner, any garage door shop will have them...they are nothing more than a piece of light weight steel in a V that's screwed to the back of the door. IF the door has gone this long with out it...its likely that it will be fine with out it for some additional time....not sure I buy it that ALL door MUST have them. With the opener...it's really important to get the spring tension right to take the opening sresses off the door.