The problem is, if I use cpanm --mirror file:///opt/perlLib/MINICPAN Net::SSH::Perl it just hangs.

Increase verbosity, get more info, maybe find out where cpanm hangs (and maybe even why)

I am using v5.8.8 built for x86_64-linux-thread-multi

good luck with that , maybe try only mirroring CP5.8.8AN: the Comprehensive Perl 5.8.8 Archive Network

Also, update all MakeMaker/cpanminus... mods

Is there an path issue that needs fixing?

Maybe

Is it a version problem (my windows box is using perl 5.18).

Anything is possible, although its more likely the module version / Config (aka path) issue