It is a big job. It's not that difficult once you understand the mechanics behind building the wall and preventing erosion.
As long as the drainage ditch isn't carrying moving water a great deal of the time, you could tackle this by yourself. You didn't say how looooong the wall might be so that will factor into the breaking-back equation. I have a good link for you to peruse with lots of PDF downloads and pictures. It's Retaining Walls I. The keys to this job are the preparation of the base, proper backfill, and filter fabric. If the job is too big, maybe a pro can 'cut' the hill properly, mark the lot, and even design the wall for you. From there, you can build the wall and backfill it. If you have the land for a lot of gravel and have a yard tractor with a trailer, you can move the stone and dump it yourself. Read up and you'll see what you're in for.
Step-by-Step guides are a-plenty, and I too, would go with stone. My best to ya and hope this helps.