Ford Wagon Range

I'll take a punt here and suggest that your car is the turbo-diesel variant with the six-speed dual-clutch transmission. The dual-clutch unit is vastly more problematic than a conventional automatic transmission and has given many manufacturers (Ford and VW being two of the main ones) all sorts of consumer grief over the years.

The unit in your car is a wet-clutch design which is much more robust than the cheaper-to-make dry-clutch type, but has still been known to fail. (The dry-clutch units on Ford's Focus, Fiesta and Ecosport models cost Ford millions in fines when they began failing at low mileages and the ACCC stepped in.) That said, the wet-clutch units have also experienced problems, but before you scrap the car or shell out $15,000 for a new gearbox (which sounds like an ambit claim in the first place) have it checked out by a specialist. In many cases, jerky progress like you're experiencing can be caused by the transmission's control module or even a faulty speed sensor inside the unit, rather than the actual transmission hardware. If that's the case, it may be more economical to repair the car.

Beyond that, I totally agree that less than 100,000km is not an acceptable lifespan for a major component such as a car's transmission.

Ford Falcon headliner replacement cost will be somewhere between about $300 and $500, depending on a few details. Those prices are based on a modern Falcon, say, a BA Falcon or FG Falcon from this century, after Ford had switched to the one-piece, cardboard-backed headliner. However, the cost could be more if the vehicle is a station wagon or has a sunroof fitted, as both these things alter the amount of material used and the degree of difficulty in removing and refitting the headliner. 

Other variables include whether you take the vehicle to a motor trimmer to have the existing headliner recovered, or you call an onsite repairer to remove your old headliner and fit a reconditioned unit in your driveway or car-park at work.

You might be able to find a second-hand replacement headliner at an auto parts recycler, but the danger is that the headliner you buy might also fail in the not-too distant future. That’s because the modern one-piece headliner – including late-model Falcon headlining - is made from a structural backing board with a layer of foam sandwiched between the board and the vinyl or cloth that you see above your head. Over time and with heat, the foam layer breaks down into dusty fragments and the adhesion between the backing board and cloth or vinyl is lost. That’s when the cloth starts to hang down inside the car.

Overall, Falcon roof lining replacement is not a difficult job for an experienced trimmer, but it is a bit fiddly and will take some time. Many owners put up with a saggy headliner, but a fresh roof lining repair will make the car look and feel brand new again.

You can find more information here. 

An engine that runs well when cold but misfires when It’s warmed up is often a victim of poor air-fuel mixture. That can be caused by an air-leak (such as the intake manifold gasket you’ve already changed) a crack in any of the intake plumbing, faulty fuel injectors, a worn fuel pump, a corrupted ECU (computer), blocked fuel line or about a thousand other things.

But in this case, knowing the Ford AU Falcon’s engine, I’d be taking a close look at the ignition system, specifically the coil pack. These have been known to fail regularly, often displaying their problems including a rough idle, once the engine has warmed up; precisely the symptoms you’ve noted. That said, rather than rush out and buy a new coil pack, have the vehicle scanned electronically to rule out any other potential source for the problem.