Hard to say for sure - depends on what else is wrong. If it is just the transmission as your major repair - then fixing it would be cheaper than buying a new car - more so if the vehicle is FREE. Only time I would consider it a bad deal, is if there was some structural damage or if you need something more fuel efficient or more compact than the Land Cruiser.
If a lot of parts need to be purchased, could turn expensive really quick. 4x4 parts are much heavier and more expensive as a function of being more robust. Parts can be hard to find. Maintenance and upkeep would be significantly higher than a smaller daily driver - 4 wheel drive eats gas, tires, and brakes.
But if you are looking for a tank and reliable (once you get everything fixed) - can\'t beat the older Land Cruisers. Especially if equipped with the inline 6 (4.0L or 4.2L) for power, inline 4 is a little weak but easier on gas, they are just about unstoppable in any weather, driving conditions. Quite a few out there with 300K - 400K miles on them with just normal maintenance.