Change all fluids. New oil, air, fuel filters ( I see that was done). Grease the front suspension and the rear leaf springs can be sprayed with chain oil ( seeps in between leaves of spring eventually).
Check for leaks. Check all hoses, cooling and fuel. Rubber ages. You might have silicon coolant pipes as mine did from new.
Gear change.....look in gomog. The crunch might be cured by new clutch fluid as it deteriorates being brake fluid, but there are other causes noted in there. New gearbox oil has helped some in the past. I had the R380 gearbox and the “ dust cap” is a known weakness. The lug for bolting in place snaps . Check yours. Usual fix is weld it back together with reinforcing lugs. I replaced mine but it took about 4 years to find one! I found hens teeth and rocking horse poo easier!. The part number is UKC3159, embedded in my memory. Fitting the new one improved gear changes. I even made a bracket to bolster the original with welded repair but the new one did the job.
Check tyres for age/condition.
Check rear brake cylinders and shoes. Check front disc and pads. New fluid. It deteriorates and absorbs moisture, hence change every couple of years.
Your front brake callipers are probably Austin Princess( yes). Pads are easy to get and they can be refurbished. I replaced mine with the Mulfab upgrade as one calliper became damaged ( pad pin lug broke off).
My first Mog was a 1993 4/4 and had low mileage and lack of use. It felt better after use. My Plus8 was a 2002 car.