Why would anyone consider doing it themselves unless they had experience in company tax?
There are many issues:

1. What income do you and dont you pay tax on?
2. What items are deductible and which are not?
3. Which penalties are deductible?
4. Which legal fees are deductible and which arent?
5. Does the company get a 50% discount on its taxable capital gain?
6. What is this imputation credit thing all about?
7. Under what circumstances will previous years losses be available for offset against the taxable income?
8. On what basis do I lodge this return---cash or accruals?
9. How do I choose to lodge it on a cash basis?
10. What special deductions are available?

No. Tax legislation is complicated, and if you get it wrong, the excuse of "I didn't know" doesn't cut it.  There are many variables that have to be considered, just like Ian has mentioned, and I would add the following -

Have you taken money out of the company and not declared it as wages?
Do you owe your company money?

Both of these questions have ramifications on how those funds are treated.

Also, are you trading whilst insolvent?

It's just not worth the risk of preparing the company tax return yourself.