These things are BIG!!
I'm sure with some dedication a working spectrograph could be made.
Some spectrographs (particularly the echelle designs) work with fibre optics. Mounting the end of a suitable fibre in a dummy eyepiece is relatively straight forward (See "Astronomical Spectroscopy for Amateurs, p 210) the trick is being able to guide the target star image on a 50 micron fibre end!!
The reflective guide plates I designed for the Spectra-L200 incorporate a couple of pinholes for just this reason. They can, with some thought, be used to construct a reflective guider assembly.
Processing and analysing astronomical spectra is becoming easier and easier as new freeware software becomes available - I recommend and use BASS project.
https://uk.groups.yahoo.com/neo/groups/astrobodger/info
Drop me a PM if you need more info.