First of all, use the scummvm provided if you want the easy way out.
Secondly, use your original discs for another easy way out, just create two bin/cue-file pairs and use this:
“Z:\>IMGMOUNT E C:\Images\MyImage1.iso C:\Images\MyImage2.iso -t iso
When mounting multiple images (useful for any application which requires discs to be swapped while it is running), you can then switch between the mounted disk-images by pressing Ctrl+F4 (by default) while your application is running.”.
Note: not tested up to disc 2!
There might be a few problems with getting the legacy version to work on dosbox, as there is CD-audio included, I used imgburn to create a bin-file of the legacy directory and then created a cue-file that had the cd-audio listed (converted to mp3, because imgburn didn’t like the original oggs).
After that you can just mount the cue as the lowest letter CD drivee (imgmount e:\t7g\t7g.cue -t iso -fs iso) and go to town.
Now, you might want to mount a secondary copy as read/write and use the installer so that you have a place for your saves, and the groovie.ini-file points to the right data directories (you can edit it), so more fiddling might be necessary.
I’ve attached my cue-file as an example.