Hi Ali,
The most common visa that is issued is the Specialist in humanities (etc) visa. It covers such a broad range of job titles. I have this visa too and my job description/contract is for admin, international communications, contracts etc for a software company. So unless you get a job as a specialist like a software engineer then a job in a publisher will probably be the same visa.
To answer your second question, currently the Alien card is separate from your visa. So I would just renew your alien card on the 22 March and if you change jobs or visa status then update your alien card after the fact. Note that any time you make a change to your visa or living situation you need to update your alien card - eg marriage, change of address, change of jobs. This is usually just an added line on the back of the card. For renewing the card, I would suggest that you renew you alien card earlier rather than later as it can take a while. So aim for end of Feb to go in. This will change in 2012 I think but for the moment just do it this way.
If you change jobs before the end of your current visa, you new employer _should_ sponsor a new visa for you as soon as you start. But mostly what happens is that they will wait until the current visa is up for renewal. It all depends if your current visa sponsor informs immigration that you have left their employ or not. Mostly they wouldn’t be bothered but you might work for a company who does this. Remember that your visa is linked to your employer rather than you. When changing employers and you are getting a new visa, it takes longer than renewing an existing visa so leave extra time. You can’t leave the country on even a holiday if your visa status is in renewal or updating. Just be aware of this.
Please note that I am not a lawyer or an expert so treat this free advice with the same caution as you would with all other free advice.