How to hide brackets and create bars over variables

I have two problems figuring out how to format my formulas properly so that when I print out the notebook the formulas look like the ones in my textbook.

So far I've got this:

$\sum\limits_{i=1}^5 x[[i]]-x$

but ideally I would want the i to be without the double square brackets, and also I would want a bar over the $2$nd $x$, and to make it the mean of the list $x$.

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In my opinion you should keep input code separate from output formatting; attempting to write your Notebooks such that input looks like standard notation but evaluates as the Mathematica code you want will usually lead to frustration. Is this what you are attempting? –  Mr.Wizard May 5 '14 at 12:03
Yes, it was 8) What would be the best way for creating a document that can be printed out that contains standard notation, but also has calculations that I can execute? –  Tim H UK May 5 '14 at 15:16
There are ways do to this, but they should be considered special-case-tools rather than standard practice. I don't have time for a proper answer now but look at Interpretation as a start. You could use my AutoCollapse code or even AutoDestruct with input cells which CellPrint other input cells containing InterpretationBox expressions. If that doesn't scare you off I can try to provide an example later. –  Mr.Wizard May 5 '14 at 15:36
I agree with @Mr.Wizard, but you could look at these examples: Representation of product with exclusions, Can I enter the traditional form for Binomial as input in an expression?. There are many others. Also, you can allow Mathematica to evaluate TraditionalForm input. –  Jens May 5 '14 at 16:05