question about cement repair

the drainage system in front of my garage pad (from a downward sloping driveway) is in need of rebuilding. I've built a small web page so you can see them... Anyway, its plain to see what the issue is. the garage pad is smooth, hard and virutally perfect. However, the cement that resides in front of the pad (in between the pad and where the asphalt starts....about 18 or 20" total) is currently pretty deteriorated.
can anyone recommend the best course of action to repair this? I'm betting that with the aid of an air hammer and chisel bit, I can quickly clean the rough/old cement away from the pad edge and release the front rail pretty easily. the rear rail is still pretty securely mounted, but I'm sure I can hack it away without much fuss.
I'm thinking the best idea would be to completely clean away the old cement from the pad side as best I can. then on the opposite side open it up back enough to get into the solid concrete again, assume prolly 2 or 3" worth past where the rail is mounted will be enough. then what???? build a form and pour?? a few question:
1. what type of cement to use? 2. what type of extraneous prep work do I need to do?? any bonding agents? anything else? 3. tricks on forming? 4. anything else I should consider?
I don't want to have to keep repairing this old girl every year....granted this is pretty deteriorated, and likely has been this way for a few years....I don't want to do a patch job, I want something a little more lasting. any ideas would be great!!
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