Ok, looks like it's already been sporterized and refinished so that will greatly reduce the amount of work that will need to be done. I forget the name of the spray stripper is that I have used in the past. Any of the commercially available strippers will work just fine. Ask your dad what he would use to remove varnish with the least amount of effort and I'm sure that will do just fine. Be very careful around that foreend tip, make sure you mask it off very well and try to stay light with the stripper around it. Oh and by the way that is a nice Argentine mauser, is the royal crest still on the receiver?