A distribution upgrade will, in all probability, not change any of your configuration.
In rare cases, it can overwrite configuration some files in /etc, but never in your home directory. Make sure to back up all configuration that isn't easily restorable. Of course, you should always back up everything.
- In case any configuration does break, don't restore your backed up configuration files. Use them as a guide to re-configure what ever software.
To rule out any incompatibilities, it's recommended that you try out the new version via a live CD. Even though it would be surprising.
I agree with DKuntz2's recommendation to back up, however - I disagree with his recommendation to restore. Restoring old configuration will cause problems at some point. The upgrade process is very smart about preserving your data while upgrading programs. They, in turn, are very smart about handling old data. The will do the best they can with your customisations and changes.
Here's how to proceed:
Back up all your data, as you normally would.
Read the Release Notes. Especially check the Known Issues section for regressions.
Try out the new version with a live cd or live usb image.
Use the provided methods to upgrade, that is hit Alt+F2 and type
do-release-upgrade, do not change your source.list file, this will result in partial upgrades, leaving old version of software on your system instead of upgrading them.
One important note though: If you have used anything like Automatix or EasyUbuntu, that is any repositories that are unsupported and not recommended, all they have done may very well break. Remove this software before upgrading, to be safe. (ref)
Please consult any of the sysadmins here on Apache, or just back it up completely. I'm pretty confident in sending you off to upgrade, very much assuming that your recovery plan won't be needed, but I can't be so confident about Apache. I've just never used it.