Two very simple to use text editors for command line are 'joe' and 'pico'. However, I would suggest instead that you use vi, which will actually be vim on most linuxes because it is a much more powerful tool. (here's a tutorial for vim, but there are others to google if this one doesn't explain what you need: http://www.apmaths.uwo.ca/~xli/vim/vim_tutorial.html
use arrows to go to the line to edit
push 'w' to go to the front of the next word until you get to 'nvidia'
type 'cw' to change that word, typing nv in its place
push 'esc' to exit insert mode
now type 'ZZ' to save and exit
The above commands should NOT have the single quotes, those just make the actual command stand out, the case is important, those are capital ZZs.
Your other option, is find the correct link to the source RPM from another computer, (I don't know your kernel version, can't link you), then use the wget program.
cd <directory to put the file in>
and then install it using rpm command line:
rpm -ivh kernel-source-version.rpm
(make sure to replace the version in the rpm command with the exact filename)