At the very outset, let me welcome you to the sickness
Secondly, let me hasten to reassure you that the very phrase "nice FJ40" is a complete contradiction of terms, since there IS no such thing. ALL FJ40s are nasty, ornery, ferocious and vicious...they only have "nice" owners.
Now, onto the more serious stuff.
FJ40s will never be the most comfortable ride in the world. They simply aren't wired that way, and neither were they designed that way, ab initio. What they ARE, is hard, uncompromising, incredibly reliable, simple, and no-frills-attached. They offer a vast choice to rebuilders with regards to a host of stock and/or modified fittings, which make them a dream for anyone with a fertile imagination. You have dozens of engine, transmission, axle, differential, and exhaust options, so pinning a ballpark figure on how much you're likely to spend will definitely vary, from combination to combination. Believe me when I say it isn't uncommon for rebuilds to exceed PKR 2 Million. At the same time, it's quite possible to just add some oils to the original mechanical set-up, charge the battery, and start driving it everyday, straight from the auctioneer's block.
In the local context, there's a vast pool of craftsmen and technicians who're experts with the FJ40 in terms of body work, engines, modifications, interiors, tops, and electricals. Also, there is no dearth of parts out there. You just have to be able to access the right areas for the right bits. At this juncture though, I must hasten to add that the FJ40 is a money pit. You'll invariably end up pouring a lot of time, energy and resources into building one, simply because there is such a huge potential and so many areas, to do so. At the same time, your rebuild will never truly be "completed". Once you'll have achieved your desired set of objectives, a new set of them is likely to evolve. So you can't really pin a certain time frame to the rebuild, either. Such, is the very nature of the beast.
Bottom line: it's rough. Noisy. It rattles. It has little/nothing in the way of creature comforts. Your wife / girlfriend will hate it. If you're single, your mother / sister will probably hate it too. But it's still THE best off-roader on the planet. 'Nuff said.
Best of luck in making your choice.