Seeking upgrade timeline advice

I work as a freelance web developer and I have been approached by a customer to do the upgrade on their Zen Cart site. I have done a couple of Zen Cart installs (but no upgrades) and custom templates, so understand the basics of the database and system, but am by no means an expert.

They have been hacked twice in the last two weeks and want to prevent it happening again. I have read the info on "If you have been hacked" and plan to perform those activities at the same time as the upgrade.

What I need to find out (so that I can give them some sort of quote) is how long does it generally take to do the upgrade?

System info:
Current version 1.3.8a (unpatched :shocking: )
They have a couple of add-ons, the main one I know of being the Sagefish CSS Horizontal Drop Down Menu
They have a custom template (correctly done using over-rides, not hacked :D )

Thanks in advance
Maree

The first time I upgraded it took me around an hour. The next few times it has taken around 15 minutes. Of course, I am a complete novice. If you are a web developer, you should be able to do it much quicker. Just read up on the template override system to avoid any trouble.

Thanks for that.