Yes you could, there is pretty much no difference. Your mac mini supports 1066,1333,1600 and maybe even 1866 MHz RAM. But you wouldn't notice the difference between 1066 and 1333 at all.
Installing Lion on the SSD?? Not that I know off. How about you just clone your current HDD. Then everything will be the same, just immensely quicker. You can then delete the content from the HDD.
You can use SuperDuper or CarbonCopyCloner for the cloning of the HDD onto the SSD.
RAM is so quick that when going to 1333 itl shave off a couple milliseconds or nanoseconds when something gets written to it. You don't notice that stuff on normal use. You can definitely notice the difference going to 1333 from DDR2 667 or DDR 133. But not from 1066.
RAM is so quick that when going to 1333 itl shave off a couple milliseconds or nanoseconds when something gets written to it. You don't notice that stuff on normal use. You can definitely notice the difference going to 1333 from DDR2 667 or DDR 133. But not from 1066.