That Time of Year Again: Self Assessment Woes

[sherbert]

As a self employed person, let's say I earned 40,000 during the tax year Apr 2016-April 2017. 11,000 of this counts as the personal allowance which I do not have to pay tax on. On the self assessment form do I enter 29,000 (i.e. my earnings minus this allowance) or the whole 40,000 (and then will HMRC automatically only tax me on 29,0000)?

Secondly, if I recall correctly, the amounts shown on the 'View your Calculation' screen that are due to be paid are adjusted at some point after the return is submitted depending on the amounts I paid on account for 2016-17 during 2015-16. Is that correct? And the actual amount you need to pay by 31 Jan, minus the stuff you've paid on account, will be shown on that first log in screen once you've submitted the return.

I did this last year but obviously the experience was so awful, I have blocked it from my memory