Hi:
The simple answer is yes you can on both counts. However, the results you get maybe disappointing. I know little about Macs as I don't use them. However, my friend has an old Ibook and the headphone socket on that doubles as a Video Out perhaps on newer Macs there is a simillar or better interface. We plugged her computer into my Beovision 1 and a picture was displayed but there were many visable lines on the picture - like an NTSC broadcast and there was lots of background fuzz (noise). This might be because the Mac wants to output to a monitor with no speakers and on headphone plugs if a contact is not used but in contact with metal a buzz can be heard. In essence it was not watchable.
You can buy a cable from Maplin for about £25 that will connect a PC to your TV and this does work as I have used one. There was no buzz and it worked fine. However, this does not carry audio so you would need to run another cable into the TV for audio. Unfortunately due to the resolutions of CRT TVs you can only really use such a setup for watching films. Text on your desktop will not be readable so if you were thinking of having a large monitor which you could use for work, this will not be the case.
That said I nw use a PC with a TV Out socket hapily for watching IPTV and viewing photos, I have an audio cable running into the back also and the sound is fantastic.
Thus it is possible but with limitations.
Hope this helps
Graham