[TYPO3-english] Importing custom content to TYPO3

[Simon]

Hi fellow Typo3-users!

I am building a TYPO3-site for a client, where I need to import data 
from a custom made gallery/shop system. I will then use the page 
structure as categories and records as image elements in TYPO3 to 
display future uploaded images.

But the problem is that I need to preserve the old element ID's (or in 
TYPO3 lingo UIDs) so I will not mess up any element data, while still 
being able to add new ID's for any future images. How do I approach this 
in TYPO3? Would I then be using for instance many-to-many relations? 
I've been wondering if I should build the whole thing from the ground 
and up, but as the old system contains hundreds of products all relating 
to each other, I'm naturally trying to find the easiest solution.

Best regards
Simon J.