Hi Steve its Jim from Brum, you already have the answer to understanding wizard features on Mach. You were one click away, good old YouTube have lots of examples on how to use them. Just type in "Youtube Mach wizard videos". The beauty of them is they do the preparation lines for you, putting all the correct G and M codes in. Just be aware that if you go back to make a small alteration check all your figures you put in as Mach default to the set display (unless you save your new settings). I have broken many cutters and drilled my machine table when I have forgot this point. The text engraving video give the best example. One thing to remember is to name the file with something relevant when you save the final program in your program folder as Mach calls them all the same so if you reuse wizard it over-writes the last one.
Regarding your stainless tube, the program you are using seems to be cutting a lot of fresh air, so will have a look at possible programs and get back to you via a personal message in the next couple of days. Unless you are retired like me so time is not a problem. I go out and do a bit of gardening whilst waiting for the program to finish.
Could you use a 25mm end mill and plunge feed down in the Z axis.
Jim