W. Salam,
First the most important thing about 4x4 vehicles, they are not economical. The more you go deep into off road vehicles, more expensive they'll become. Bigger versions go around 6km/l.
Pajero Mini is an awesome vehicle until its not modified by desi mechanics. Being an owner of one for over 2 years now, I can say without doubt. You can read my other thread where I've shared most fixes in my vehicle.
1100cc engine came with Pajero Jr. which is almost non-existent. You'll find modified Pajero Minis with Jr.'s engine in them, but I'd not recommend you as you'll need to be half-mechanic yourself to deal with its regular breakdowns.
I'd recommend you to get newer model of Pajero Mini 2010+ model which is later rebranded as Nissan Kix in 2012. They have over-drive (4th gear), so fuel consumption is not bad (auto version). Being a 4x4 vehicle, its gear ratios are not as regular city cars. So you will most likely get around 10km/l average in city.
Top speed can go to 100km/h easily on these models, mine is 5 speed manual version, and I've gone upto 120km/h on motorway without any issues. My trip was from Karachi to Islamabad, then to Azad Kashmir. Pajero Mini is pretty stable at 100+ speeds as its pretty heavy compared to city cars of this same size.
You can go to any place in Pakistan on Pajero Mini as long as its maintained well and all functions work. Consumable spares, air filter, oil filter etc are easily available in big cities, and you should always keep one new for each of them in vehicle, along with couple of radiator pipes (recent experience).
Do remember, this is pretty small car, and best suited for 2 adults only, rear seats are not comfortable for long travel. Rear seats fold to make a big flat surface to load up luggage, thats how I mostly keep them.
I hope most of your questions are answered, if you have more questions, sure reply below and I'll try to help
Best regards.