I figured it was, but you never know. :)
Your monitor also has a vga plug in also, if you can borrow a cord, you can verify that it works by useing that plug from another computer.
The cord looks like this.
Or you can find another computer that utilizes a dvi connection, which most do nowadays.
Now if after all is said and done, and you have confirmed the monitor is fine, you just need to change out your video card. The cost really depends upon what you currently have and what you replace it with.
I am guessing your mac is a G5 tower, but you never really did say what model it was.
If you would give me that, I can provide more information.
Your monitor does also have an svideo input, so if you had a portable dvd player, you could test it that route also. Also has composite, so if you had an xbox 360, could test that route also.
Just tossing ideas at you.