When I updated my site, it was kind of a pain too.
In fact, I did just what you did...created a 2nd copy of my site and a 2nd database to mess around with until I got it all working.
Here's the how-to from help.mamboserver.com that details the process. Definitely read it.
The basic process is:
1) copy new files over the top of your old ones
2) upgrade the sql via the path recommended above
3) rename configuration-dist.php to configuration.php and reset up all your parameters (either in the file itself or via 'Global Configuration') -- you'll need to set host, dbuser, dbpassword, dbname, etc. all over again...and make the absolute & relative paths accurate to your 2nd copy (not the original)
4) upgrade a number of components/modules that are not 4.5.1 compliant
Once you've got everything operational, do consider running the upgrade to 4.5.2.2 - it's worth it and much easier.
