I have to admire you for your desire to do this job yourself but from what I've read, the reason there are specs and permits and such for septic systems has a lot to do with a lot of things. Among them are DYIers.
The code for building these things vary from municipality to municipality. Soils vary, climates vary, and topograpy varies. In some cases, it may be illegal to rebuild a system. That's why when you go for a permit, a site inspection is so very important. I wish I could assume 'things' here but there are way too many assumptions for me to make. At best, I suggest you perhaps be-friend someone in that line of work to see if they'll consult you on the job. Maybe you pay them $50 per hour to do everything except the excavating and plumbing. You should have a permit and the required inspections at the least. Again from what I've read, many systems are doomed from the start due to professional ignorance and the like. This is just the impression I'm getting from what I read.