How can I replace canned tomatoes with fresh?
Tomato Sauce made from fresh garden tomatoes can be very much more flavorful than canned tomatoes. If you have an abundance, it can certainly be a delicious improvement. I would follow the directions given in the previous answer for peeling the tomatoes, with the additional suggestion to plunge them in ice water immediately following the boiling water bath. They are much easier to handle that way. The recipe may call for reduction of the sauce, and this can be done with fresh as well as with canned tomatoes.  I have also made tomato sauce from fresh tomatoes by cooking down the unpeeled tomatoes until they are soft, and then pressing them through a food mill. After that you can reduce the sauce with additional ingredients  - olive oil, garlic, onions, herbs as desired.