I bought my 2000 Ford Ranger brand new. I currently have 139,000 miles on it. I have always changed my oil before I hit the 3000 mile mark. I have not any major problems. I tuned it it myself at 100,000 miles. I have had the cooling system flushed 2 times and the transmission flush 2 times as well. This is just maintenance items that I personally like to take care of. My front brakes lasted well over 100,000 miles and the rear drum brakes I changed at 105,000 miles. It is a great truck. I wash my engine every 2 months at the car wash (I cover the electric parts and so forth of course). My paint still looks nice, shiny and clean. Next time I will get the 4x4 for winter driving.
The reliability of the engine and components.
None really. As long as you take care of it, change the oil etc. and stick to the recommended maintenance schedule it will last!