I know - wikis have a learning curve attached to them - but you seem to be doing very well so far. :-) To respond to a message on your talk page - simply edit your talk page, just like editing any other page. Or, better still (and this is quite normal - etiquette even), edit the talk page of the person who left you the message. If that person has signed their name, you can go to their user page by clicking on their username, toggling to the "discussion" (talk) page, and editing that. There is also a feature on talk pages where you can click on a little "+" beside the edit button, which will automatically start a new section on the talk page. The main advantage to responding to messages on other people's talk pages, rather than your own, is that when that person logs in, they will get a "you have messages" notice near the top of the page - as you possibly already noticed yourself.
No problem about the page rename - if you ever start a page with a title that has a typo, or that you simply want to rename, you can always use the "move" button beside the edit button (you need to have been logged in for a few days - I think it's four - in order to use this feature). Choose the name you want to move the page name and execute the move - it's dead simple - and don't worry, as with everything, it can be undone/redone. The only thing to bear in mind is that this will leave a "redirect" page in the old pagename - which can be good if many pages link to the old page - but if no pages link there, it can be simply deleted. You can always request a page deletion by messaging me - by email or on my talk page - or adding the page to http://en.wikiversity.org/wiki/Wikiversity:Requests_for_Deletion
About the philosophy link from the search bar - this could be a number of things. If you type in "philosophy' in the search bar and choose "go" (the default option) you get redirected to the School:Philosophy page <http://en.wikiversity.org/wiki/School:Philosophy>. Is this the one you are trying to add a link to your page from? You can add a link to your page by adding the page name within double square brackets on the page, which will add a link to your page. Note that, for internal Wikiversity links, you only need the page name, and not the full url, so, to add a link to your page (from any page), you would add Historical Introduction to Philosophy/General Introduction to any page within Wikiversity. More help on linking can be found on: <http://en.wikiversity.org/wiki/Help:Link>. If, however, you added 'philosophy' to the search bar and clicked "search", you would be brought to a list of pages that are about philosophy (though the Wikiversity search capability is not comprehensive,a nd some pages may be missing). To ensure that all pages about philosophy are findable, it's a good idea to add at the bottom of your page, and then every page that links to that category can be found at: <http://en.wikiversity.org/wiki/Category:Philosophy> (which also contains some more specific sub-categories).
Regarding "fair use", this is when things get *very* complicated. There is huge debate about whether wikimedia projects should claim "fair use" - particularly as this is not applicable in every legal jurisdiction (ie country), and Wikimedia projects are very much an international initiative. Some projects do allow fair use, and some don't - see this page on meta: <http://meta.wikimedia.org/wiki/Fair_use>, which has links to individual projects' policies. We haven't worked out a policy on Wikiversity yet - but the best option is *always* to use free/open content (ie content which does not have any copyright restrictions). This, after all is a large part of what we are doing across all these open content projects.
I realise this all might be complicated - and if you've any questions, please don't hesitate to get back to me. This is much learning to be done in participating in a project like this - particularly at the beginning - something which might be interesting to reflect on as a learning activity - I'd like to improve http://en.wikiversity.org/wiki/Wiki by actually using our collective experiences - if you're interested at all. In any case, welcome to Wikiversity - and genuinely looking forward to learning more about philosophy - it's a large part of my preparatory work for my PhD.
PS: If you want to link to your Wikiversity userpage instead of your wikispaces one, you can add User:Mlanaduncan from any page - it might be good to put some text - even simply "hello" - on your userpage, so that your userpage is a blue link, rather than red (which indicates that the page doesn't contain any text yet).