As Andy suggested, nows the best time to pop a set of seals into your diff to keep it leak free, whcih brings you to the only thing that would need locking, whcih is the nut inside the flange for the input shaft.
On the diff the dwo driveshafts just bang in like normal frongwheel drive driveshafs with snap rings securing them. The input shaft of the diff has a male spline one it, onto which is slid a sleeve with a female spline with a four bolted flange flange for the propshaft to attach to. this needs removing to do the seals. It is bolted to the input shaft with a nut, which is frackin tight. To get the nut off to do the seals, you'll need to secure the flange. When I did mine I put a bolt through the flange, and a spanner on it spun the spanner around to bind against the neck of the drive flange and let the spanner press up against the floorpan. With the new (to you) diff on the bench, you could probably secure the drive flange in a vice or use a stilston, or such like - Im sure you'll figure something out.
The nut I am on about is TXV100000, top centre in this diagram:
The seals me and Andy are on about are 2x TOC100000 & 1x TZZ100150 in that diagram. Less than a tenner on eBay:
https://www.ebay.co.uk/itm/1-Input-2-Rear-Back-Diff-Output-Shaft-Driveshaft-Oil-Seals-For-Freelander-1/233335129321?fits=Model:Freelander&hash=item3653db84e9:g:z8AAAOSwcIpee95s
Put it in with new diff mounts, as these motors tend to eat the front diffmount, which is a minor PITA to change. The front one is the most important one and is about eight and a half quid on eBay, and you'd be about thirty quid for a complete diffmount 3 piece set. But the side mounts arenae as bad to fit, so if you are feeling the pinch with COVID cutting your earnings, or just feeling stingey, you'd get away with just doing the diff seals and the front mount.