Is it possible to just insert it into my mac? Will it start downloading Mountain Lion from the internet and then will I be able to restore from my time machine backup?
I do now have a HDD enclosure and I will be upgrading to a samsung 830 ssd basic kit.
You have to format the HDD at least, and as far as I know, currently you can only download Mountain Lion from the Mac App Store and not via Internet Recovery.
Why not download ML on your current Mac with your current HDD, make a bootable installer (many, many guides available on how to do this with a 4 or 8 GB USB flash memory thumbdrive), insert the new SSD, make a clean install of ML (which includes formatting the SSD correctly, again, many guides available for this and for Lion (same procedure))and then either use Setup or Migration Assistant to import the data from the Time Machine backup.