No PITA, just a different process... You can download the ML app/installer from the App Store and install/upgrade your current OS on your boot drive.
If you want to clean install to a different drive you need to make your own ML USB boot drive. You will need a spare flash drive or external hard drive, to keep it simple use this tool to make the boot drive...
Lion DiskMaker
Finally boot from your new USB boot drive and install ML on any internal or external drive that you wish. Make sure you run Disk Utility from the boot drive first to partition and format the target drive as needed.
Also unless you plan on running the SSD as an external drive you might as well install it in your laptop before installing ML, doing so will make the install go quicker (unless you are using Thunderbolt). I don't know about all SSD brands but I have an OCZ and they recommend that you never connect the drive using a bus powered USB enclosure, doing so can corrupt the drives firmware and you must run there boot tools to reflash and secure erase the drive.