I am an oral surgeon...
and you problem comes down to the degree of decay. The shallow decay has a much better prognosis. The deeper it is or the closer to the nerve of the tooth, the more likely a root canal treatment will be required. That hard to assess clinically or on an x-ray. Sometimes that decision is best made after cleaning out the decay and seeing what is left. If the wisdom tooth in that area is present I might be more inclined to recommend to restore it, rather than manage the empty space. If it is the last one in the row and significantly decayed, I might be more inclined to take it out.
I would be all for seeing you get a second opinion... The more heroics to save a tooth, likely the poorer the long term prognosis. Keep in mind that this opinion is from a guy who makes his living taking them out...
-John