No doubt this has been asked many a time but I couldn't find anything quick enough ...

I have been developing stores with OSCommerce for quite some time but lately have been drawn towards zen.

I have installed and played around with the back-end but before I commit I would like to ask a few questions, if I may.

Adding contributions
Believe it or not I couldn't find any info on actually adding contributions!
I understand that, most times, instructions come in the package 9or at least they should>) but I have downloaded a few that just contain the new file with no instructions etc. So my question is, where are the instructions?

Payment
How easy (bear in mind my usage of OSC) is it to implement payment through HSBC and Paypal (UK)?

Customisation
Depending on your knowledge of CSS, I am thinking zen is fairly straighforward to adapt/ customise as much as you desire. Is this correct?

OSC conversion
Bringing in a database from OSC to Zen either through phpmyadmin or Easy populate. Easy/ hard?

Thanks.