Enabling .htaccess

Sorry - this is a duplicate post to one I initially posted in the 'using your readynas' forum.  I thought it would be better here than there.

I have an older ReadyNAS NV+.  I'm trying to move my personal web server onto it.  I've installed the add-ons for php5, curl, apt-get and ssh enable.  All the add-ons are running great.

I've created my web folder, got the permissions set etc. and apache is serving my website perfectly.  That is until now when I started trying to password protect some pages.

SO... I've made all the necessary changes to my httpd.conf file but page loads in the protected directory fail with a 500 Internal Server error anytime the .htaccess file loads.  Rewrites etc. work within .htaccess but as soon as I add the AuthUserFile directive it fails.

The error log shows the following error 

Apache .htaccess: Invalid command ‘AuthUserFile’, perhaps misspelled or defined by a module not included in the server configuration

This error indicates that I'm missing mod_authn_file.so at load time.

So... I edited the httpd.conf file and sure enough that module is not loading.  I would just add it at load time but the module is missing.  I've done a find / -name for the module but it's nowhere on the drive.

The version of Apache running on my ReadyNAS is 2.2.6 - so it's quite old.  

My question(s) is (are)

1 - is there a way to force Apache to grab the missing module from the repository

2 - is it safe for me to upgrade the version of Apache running on the ReadyNAS or do I risk losing FrontView

3 - if it's safe to upgrade what would the preferred method be?

Thanks in advance for any help.

mark