As was said, there are editors at many levels and prices. If this is a first major project, you might look at asking for about $90 per hour just for editing purposes. If you are being asked to film as well, thus your entire day is being taken up, then you need to set your own day for hire rate which could be from a couple of hundred to a grand or more depending on the client and yourself. If there are costs to you they should be listed on a spread sheet to show the client just what your expenses will be and then add in your own rate on top of that. All expenses should be paid by the client. They may include rental of lighting( which you can supply, audio systems and mics ( which you can supply), cables, studio, tapes and music. These are not free and they really do not have to be 'thrown in'. It is up to you. As Wags said, don't forget reproduction costs.
Now, if you are producing something and therefore, will be in charge of marketing your own stuff you must set a reasonable price for the product and figure out how many units you will have to sell just to break even for both your time and expenses. For example, most tutorial discs sell for between $49.00 and 90.00. Thus, we are talking of lots of units needing to be sold before you are back in the black.
Don't undersell yourself or oversell yourself either. I remember getting a call several years ago from someone who wanted to buy a film I had made for a Xmas gift for someone. The whole film was about 6 minutes and I said $90.00 thinking that with all the time and expense that went into it that that was reasonable. Like heck it was, they didn't buy and I learned a lesson. The public is not responsible for your time and efforts, just a single copy of the product. It is the client who sponsors the production who is responsible and not the, hopefully, many individuals who will buy it.
My more than 2 cents
Steve B)