If the stars smile on you, everything works the first time :)
To run mod_rewrite in htaccess, make sure your server says
It's probably there already. (It was in MAMP.) The default setting changed between 2.2 and 2.4, but you shouldn't need to change anything.
mod_alias is part of every Apache installation I've ever heard of, and it isn't as persnickety as mod_rewrite. It's also not as powerful.