How to handle custom changes in code?

[hmmm]

Hi,

I'm pretty new to virtuemart and webdev in general, but at the moment trying to get a shop going. One of the things currently on my mind is how to handle (required) custom changes in regard to be able to upgrade. I know i can do a lot with the views override, but things like changing the checkout process, changing the facebox, ....

Are there any best practices how to tackle this to keep upgrading and updating smooth?

Thanks in advance!

[PRO]

to change the facebox, you move the files, and do not link to vmart scripts.

what do you wanna do to the checkout?