I have rootsh installed and have the same command lines as you showed.

I deleted old files and downloaded the two new files into MyDocs and renamed the files without.dep so only libgssdep

Then again opend xterminal:
sudo gainroot
cd MyDocs
dpkg -i libgssdp.deb
/bin/sh: dpkg-i: not found

I do not get the command line:
dpkg: error processing libgssdp (--install):
cannot access archive: No such file or directory
Errors were encountered while processing:
libgssdp

Its strange as i read most people can install

Thanks for your replies sofar!