Bad characters after upgrade awhile ago ?

I have the lates v of wordpress now but awhile back when I upgraded it changed spaces and ‘ characters to ? and other odd characters I have read all over the net others with this prob + their solutions but nothing works for me, I edited the config php and then they disappeared but then I got diamonds with ? in them. My host says if he drops the db I will lose all of my stuff and this happened a few mons ago only recenlty I started to notice it, I was thinking of manually editing it but I have 500 some blog posts. If someone could help me I would really appreciate it