The problem with fixing it RIGHT NOW is that the OCR errors can be pretty consistent some times, R becomes E. If you just fix it at once, you will fixing it over and over again. If you at least read for a while you can fix these sorts of repetitive errors only once.
Sigil book view is not so hard for reading.. have you noticed the slider to increase text size? You can also drag in or out the size of the display windows to make it less wide and maybe easier to read that way.
I keep a small piece of paper inside the back of my Sony Reader cover and note problems there so I can search for them and fix them later, not interrupting my reading. I find that if I try to read and fix at once the enjoyment of it is gone and all it is work, one problem after another.