DiskSalv is available from
http://aminet.net/disk/salv/DiskSalv4.lha . (I wouldn't suggest using DiskDoctor as it can make the problem(s) worse.) Also
http://aminet.net/util/arc/lha.run so you can decompress DiskSalv.
As far as going to Workbench, you'd need to get eg. a Kickstart 3.1 ROM image and Workbench 3.1 ADF, try googling for them.