Its easy, done it a few times, loads of screens with platform/train information etc.
Just double check which station your connecting trains are form. The Eurostar is always arriving and departing at Lille-Europe, many of the connecting TGV services are also from this station so it is an easy change if your onnection is also from here. But some TGV services operate from Lille-Flandres which is 5 minute walk, its well signposted and easy to find, just double check your tickets so you know where your going!