Ow! it sounds and looks like your Freelander has had a pretty hard life in the transmission department. You are in for some expensive bills and depending on how much you paid for it, you may want to think twice about actually getting it back on the road.
We all know that getting your money back is easier said than done if the seller does not want to play fair.
It looks like the first thing to replace is your IRD. This might be the odd occasion where it could be best getting 1 from a breakers for 2 reasons... (1) with loss of front and rear wheel drive, your IRD may not have an exchange value with a reconditioners, so a reconditioned unit may work out very expensive. (2) you may be able to arrange with the breakers that you can get a refund if the unit does not work well, or if once installed you find problems with your gearbox.
If you install it and it works OK in 2WD you'll be back on the road and be reasonably happy. You can then choose a time when you get a recon VCU and try putting it back as 4WD - if the crown and pinion gears look OK and there's no/little play on the rear pinion, you should be OK. At worse you'll then need a recon IRD and can use the breaker's unit in exhange or your original and sell the breaker's unit.
If you install the breaker's unit and its obvious there are gearbox issues as well, then you can consider getting your money back and whether it is worth getting the car back on the road anyway.
Getting the IRD off and on is much easier/safer if you can do it from an inspection pit.
Good luck!