You may want to hold off for 24 hours and get the new 1.7.5 which I will be releasing later tonight.
The key is backup both the files and your database before anything
Then extract the 1.7x installation over the existing files
I dont think there are any db changes in 1.7-> but would be wise to diff the tiki.sql files anyway.
rerun ./setup.sh just to be sure everything copied with correct perms
maybe empty the contents of templates_c/ too
That should be you.
If you want to goto the Development 1.8 release there is a page for that Upgrade18 i think.