OK, it looks like there is a standard, 7200 rpm Hard Disk Drive (HDD) inside the machine, and here is how you remove it:
https://www.ifixit.com/Guide/iMac+Intel+27-Inch+EMC+2429+Hard+Drive+Replacement/7555
Hence, you should just be able to install inside one of the empty slots within the Mac Pro you plan on getting. However, if need be, you could install inside an external 5.25" case, and connect it to one of the ports on the Mac Pro. 5.25" external enclosures with a fIrewire 800 interface are somewhat common, and as long as the Mac Pro has at least one Firewire 800 port, such a setup will be decently fast, what with the 7200 rpm speed and the Firewire 800 connection.
Not sure about the RAM, as that would depend upon which Mac Pro you purchase, and if the iMac's RAM is compatible. And, via the site
www.ifixit.com, did not see anything about the Super Drive, although according to this:
"By default, it is configured with 4 GB of RAM (1333 MHz PC3-10600 DDR3 SDRAM), a 1 TB (7200 RPM) hard drive, a vertically-mounted slot-loading DVD�R DL "SuperDrive", and AMD Radeon HD 6770M graphics with 512 MB of dedicated GDDR5 memory."
it seems to have a "standard" SuperDrive.
Now, when you purchase the Mac Pro, it would be best if you could find one with a very recent version of the Mac OS. Also, not sure what you plan on doing with the iMac's drive inside the Mac Pro, but if you were planning on booting the Mac Pro from it, that might or might not work, as if the OS on that drive is one which the Mac Pro does not support, then you will not be able to boot from that drive right away.