Two months ago I got a new kilo WT after receiving suggestions from some of you on this bike. It's great so far, although the stock 48x16 gear ratio is a bit hard, especially on the few steep sections of my commute. I was thinking of converting it to something like 48x18, which people seem to suggest and which seems to be about my ideal gear ratio for the commute (as determined by comparing with my road bike).

My noob question is, how do I switch out the gear? Can I just buy a freewheel like this and swap it out with my old one?

Will I need to get a new chain too? Will I need any special tools? I've done cassette changes, chain changes, etc. on my road bike before, but never really did any work on my single speeds and want to make sure I'm not overlooking something stupid.