bert,
Seriously, if you want a "wham bam, thank you mam" experience of the cape, the tour guide experience is for you - especially if you only have a very limited time frame.
If, on the other hand, you want to take your time I would recommend against it, as spewa said, get some guides & read them.
If you are worried about tackling the cape by yourself, start a thread here or elsewhere stating when you are going etc, you will probably get a group.
Or lob into one of the caravan parks in Cairns, throw out that you are looking to tag along with some people, who knows who you will meet.
Lastly, do it yourself but when you get to a difficult bit, water crossing etc, just have a cuppa & wait for someone else to come along, I'm sure they will keep an eye on you etc.
All the best,
Hem