Upgrading - My understanding

[manguish]

Right here's my understanding of the upgrade process WITH hacks installed.

1. I know when i upgrade, i lose ALL PHP changes to my files. Hence any hack with php changes - is gone.

2. When i upgrade after overwriting all the php files, using the upgrade script - it changes the database. Will this alter tables and the like for hacks installed? If not, when i go about reinstalling the hacks - do i just leave the tables alone? Or do i need to back them up and overwrite them once the hacks is reinstalled?

3. Here's my assumption - from what i've picked up - Once upgraded, the upgrade DOES NOT ALTER ANY CUSTOM TEMPLATES. So custom templates are left well alone. HOWEVER - it does reset NORMAL templates, so any normal (header, footer etc) templates i've changed, need altered again.

I'm sure there's nothing else, but if there can someone enlighten me.

Sorry for having to go over this again - i just want it straight in my head
before i go about this.

Thanks for your time in advance.

Chris.