Depends on the system model - 17R SE covers quite a few different ones. Some systems require a daughterboard for the mSATA drive that won't be there if you didn't purchase the system with the drive. All of them require a lot of disassembly to get to and install either that board or the mSATA drive card.
There are other options they may consider:
Let you upgrade to a full 2.5" SSD. If you have a "3" or "5" series model (the four digit number of the model - on the BIOS screen, F2 at powerup) you can have only one internal 2.5" drive. If you have the "7" series model, you can actually install BOTH a full SSD and a spinning hard drive.
Or, ask them to upgrade you to a Seagate or WD SSHD (solid state hybrid drive), which will have a built-in cache (i.e., the hard drive has its own caching SSD).