Theres a pretty good size spring inside, if you have a way if keeping the case halves aligned & the diaphragm free of wrinkles while you squeeze the case together & clamp it...... then go for it.... Typically it's done on a special press designed to hold the parts & allow you good control of all the components....
Either clean it as best you can, paint it & live with it.. Or send it to Booster Dewey....
BTW 71 boosters are typically finished in yellow zinc.. Booster Dewey can provide that finish...