All of those things are fixable by yourself if your handy with tools. Being an owner of both a 1.8 and KV6, the 1.8 is pretty simple to work on, having worked on the KV6 including having done the timing belts with the kit and removing the engine with auto box attached. For the water leak at back, it's probably the rubber seal that runs from left to right at the top of the tail glass window. It's hidden from view by the piece of black plastic exterior trim, just look underneath that trim and you'll see that rubber. That is supposed to be flush with the glass and seal but over time the seal weakens. The correct way is to remove the trim piece and renew a few components i think there are also several lokut nuts. A far easier way to do it, that worked for me, is that run a bead of suitable RTV sealant, use the appropriate sealant, black in colour to match the seal, suitable for outdoors and glass/rubber/weatherstripping, along that rubber seal. Let the sealant set and once it fully cures, it will solve the leak. The sealant will replenish the seal where it has failed. Note, your leak could be from other sources but this is where mine was coming from.The sealant won't be visible as it will be hidden by the plastic trim piece just like the rubber seal. Buy an RTV that comes with that plastic applicator funnel what the term is i'm stumped..! The applicator things let's you zero in at tiny places like the area underneath the plastic trim where that seal is.
If you have a slipped liner, then this is what I recommend if you want the 1.8 Freelander to be a reliable ride for you. Remove the block and head, buy 4 new liners, and take the block and head to a good engine reconditioner. They can machine the head + block and fit the new liners as well as seal them. They will also advise whether the block should be scrapped or whether they can pack new liners and machine it, good to go, etc. While at it, they can also fit the new MLS head gasket with new oil rail and head bolts. Then you can do the water pump and thermostat, etc, when you get the motor back. Most of the other issues are lesser, that is the central one, the liners. If one liner has slipped, it will cause you all sorts of issues unless you get it addressed. It will probably also be loosing coolant as the liner seal will have been damaged (the freelander uses wet liners, thus seal between coolant and liners) thus overheating.
That's where i would start.
Is it worth fixing? I would say yes as it can be fun knowing you have done a lot yourself, and pretty satisfying driving it afterwards knowing you have fixed a lot of it yourself. That's my opinion though, and that comes from someone who owns 2 Freelanders the KV6 and a 1.8.
