i was wondering wat i need to have replaced on my 03 trailblazer. ive heard that i need to change my fuel pump and also heard fuel level sensor. so im wondering which one is causing my fuel guage to always read "E"

 

You have an 03 like me...
I have noticed that the early TB's if the needle marks E... many times its due to sulfur buildup in the tank..
later models like 05 and up- had a slightly different fuel level sender that did fail.
In your case.....
Try a bottle of techron fuel system cleaner. Use techron-- not some other brand....
This has stuff to clean the sulfur and help the fuel level sender begin to read correctly...
If it still fails to work-- then it will be time to change the fuel level sender....
BUT if you have high miles--- you may as well swap out the fuel pump since you have to remove the tank to get to both-
Here in Los angeles... at 133,000 miles I changed out my factory pump. (The level sender and fuel pump worked fine- I just wanted to change it before it failed on me somewhere in the middle of mexico- as I was taking a trip down there at the time).
Total cost with pump and stuff was about $330.
I called a local dealer to ask how much they charged for this same job.. I was quoted about $1200.

so try techron- and if not-- then try the fuel level sender swap--- or the pump and level sender as a whole..
I have seen 1 case--- where an owner of a TB- changed the sender and pump-- and the needle was still off...
in his case--- he had a bad stepper motor in his dash....