I'm getting a blank screen on checkout after installing F&E Checkout (over 167 files!), bummer

For files that already exist, i backed up first and then just overwrit (is that a word?) with new files.
is that what i should have done? or, in the case of something like header_php.php, should i open both the old and new and then combine??

thanks for any help on this

one error i was getting was a function undefined error. i geuss you can't search for a function to find the problem if it doesn't exist (not defined) 'doh!