The "recovery system" is sometimes an image of what was on the disk when it was purchased. If that is so, then everything added since then would be wiped out. You might want to read carefully what kind of recovery system it is
Even if the volume is unmountable by you at that computer, someone else might place the disk in another computer and get access to its contents, allowing at lease a recovery of the data. They might even get it to mount.
This would probably be the safest route, since it would not have to execute any of its software, including a functioning OS
There are a lot of good software applications for this. My advice is to not try to make it mount under its own power. Let it be the slave drive and another OS be running during the analysis and mounting/recovery.