It's up to you. If you KNOW that it was taken care of before/while you owned it, you can go a bit further on the water pump and timing chain. As long as you changed the oil at 3000 miles on the dot, you should be fine. Another thing to check is your coolant level. If you have to add some every once in awhile, your water pump is probably on its way out. Last thing to check is to look into the hole under the oil cap. If it looks brown, thats ok. Black and crusty means you need to change it ASAP!
I know, as soon as I figured that out I said dammit, fukin Kyle was right.