Questions from Mac newbie

Hi all, I have been browsing these forums for a few months, and recently just bit the bullet and purchased a new IMac, being an Intel guy my entire life, this has not been an easy transition. I have a series of questions that hopefully you can assist me with.

My OS is 10.6.7 and my IMAC has 4GB memory and a 3.2 Ghz Intel core i3 processor.

1) On Safari, it seems every hour or 2 I lose connectivity to certain sites only, seriously I am trying to go to one site and it says not connected, but when I go to a different site I connect. I attempted it with firefox and same issues as with Safari. But, when I turn airport off and on again I can connect again. If it didnt do it 10 times a day, I wouldn't be so concerned.

2) When I left click anything it refuses to open, yet when I right click and select open it opens. This is especially bothersome in Itunes, when I cannot open anything left clicking, it shows me the root show folder but when I attempt to open it to view individual shows, I am unable to do so.

3) My Application icon in the Apple version of the program bar on the bottom of my screen is not there. I am unable to drag programs into it to get them to work, How can I get the Application folder back where it belongs?

4) It seems my IMAC is running extremely hot, especially on the top, should I be worried or is this normal?

5) I know people claim you dont need Antivirus or spyware protection, but my day job is computer security with Windows based OSes, so is there any good programs that would help me make my system more secure/.

Thanks for your help, and please go easy on me for not knowing the Mac "lingo" yet, I am still learning.