What is the process that a person has to go through to be on the Australian senate ballot sheet? Is it any more difficult to do so independently?
To become a candidate for a party then the preselection process is determined by the rules of whichever party it is and they all have different selection processes.
To run as an independent, all you need to do is fill in the nomination forms with the AEC, meet the Constitutional and legislative requirements (in particular section 44 of the Constitution), pay the nomination fee (currently $2,000.00) and provide signatures of electors proving that you do have enough support for some kind of attempt (I believe it is 100 electors, but I haven't checked the AEC website for this detail). The drawback of doing it this way is that you don't get your name "above the line" and can't lodge a Group Voting Ticket (GVT), which means none of the parties will do deals with you and unless you have massive popular support (e.g. Nick Xenophon) then you don't have much chance of getting elected. You'd be better off lobbing kangaroo poo at your mates and joining a 4WD club/party. ;)
There is an option to create a non-party group which gets an "above the line" option. In this year's election column T on the Victorian ballot was an example of that with Joesph Toscano and Beth Matthews. They were able to lodge GVTs like all the other parties.
Getting back to the parties, the Constitutional and legislative requirements are the same. Party candidates, however, do not need to provide a list of signatures from electors because they are already covered by the membership of their political party when it was registered (a minimum of 500 members on the electoral roll).
There are also a bunch of handbooks and guides on the AEC website which go into this in more detail.