I would absoutely not attempt to restore the painting yourself. Painting restoration is a form of art in which you must be unquestionably expert in order to end up with a good result. If the painting is of any value you can EASILY end up destroying the painting and the value of the painting. Please do not attempt to restore it yourself! Now in response to your specific questions:
1) Yes, it could definitely hurt the value of your painting to reback the canvas if you are not an expert in restoration.
2) Do not attempt to put anything on the painting to "protect it," or to "restore it." You will end up destroying the painting.
3) No there is no "uncomplicated" way of determining accurate valuation sans bringing it in to a bona fide art appraiser and having it valued. You may be able to get an approximate value here by placing an appraisal request, but for a painting such as this I would definitely recommend seeking an expert to appraise it.