10w30 is what I would recommend for a 8 year old engine.
On the oil cap it says "5 W 30".
5w30
It is located either on the right or left side of the block depending on model. Low usually close to the oil filter its self.
Yes
motor oil
You didn't say which engine you have but Chevrolet's oil pumps are located inside the oil pan.
trans or oil? oil is in front left. i dont think the 98 blazer has a trans dipstick. Instead, there is a bolt on the side of the trans.
5W30 weight
This sensor is at top rear of engine, next to distributor.
It is probably the oil cooler lines.
Under the front, behind the bumper.
A Chevrolet Blazer with a 4.3 liter vortec engine will take approximately 6 quarts of oil. The recommended type of oil is 5 W 30.