Our site (The Open University) is particularly large so wouldn't be a fair comparison as we have 100's of collections and 1000's of tracks and a small team of people that could work on the migration. However I've taken a look at your site and the main issue you'll face is the structural re-organization.
The new iTUPSM has two ways to create 'Pages' of 'Collections'. The first is automatic and that is via the iTunes U categories, so provided you have at least 1 Collection under a category (might be 3, but a quick look at the documentation suggested one was enough) iTUPSM will automatically create a page for that category and a link in the menu structure on the right of the home (provider) page. The category pages themselves can have a banner added. The key thing to remember that these pages uses the iTunes U categories and if you want your collections to appear elsewhere with iTunes U you need to have categorized it and so these pages will appear.
The second way to create pages is via 'tag' pages, these are done by 'tagging' Collections, say for example 'Research' and then you can (it's optional) create a 'tag' page that includes all collections that match that tag. The tag page can include banner artwork.
Now the great thing about tags is it means a collection can have more than one tag and thus can appear in more than one place, so if you have some Research that's about Arts you could have it appear under a tag page about your Faculty of Fine Arts and also on the Research tag page.
It will be this 're-structuring' that will take time but if prepared in advance, together with some 'experimenting' in iTUSPSM the actual implementation of the conversion should go smoothly, particularly if you can commission artwork around the new banner sizes relatively easily.
The only other advice, but I don't think it's applicable to your site, but mention it for anyone else that it might be is if you were using group tabs in your Collections as these get separated into separate Collections and you might have a lot of work getting the now individual Collections making sense.
Regarding contributors I can't speak from experience as when iTUPSM first launched the concept of 'contributors' didn't exist and so all our current users are Admin, but it's also a small team so they work together . However I believe you can assign contributors to individual Collections, the relevant details are here in the iTUPSM.
Finally you might read this section in the iTUPSM which looks to pull together the steps involved in migrating your site.