Humm I'd certainly find out what discussion were had Helen. It might even be that the LD account manager offered certain types of help at no extra cost in order to get this deal.
Hard deleting users will be a problem if you are using SQL. LD has too many referential widgets in it to allow for deletions. MS have put quite a low number on the maximum allowed and stop the deletion with a 'too complex' error. Maybe more recent versions of SQL have improved this. You'll probably have to turn those off to do the deletes and that can be dangerous as you might end up deleting someones record when it is in use. i.e. you really do need to have those referential checks in place to make sure you are doing safe deletes.
But on the plus side if your manager wants you to do all this rather than pay our friends at LD, you will learn a great deal!
It's a shame T2L doesn't allow you to pick more things you want to sync/don't sync - that would help a lot.