To inspect the mast and spreaders you will need to remove the paint. Sand blasting wouldn't be the best way but blasting with other less powerful abrasives could be a good way to clean off the paint so you can then inspect the details and look for cracks. Sand itself under pressure can make a hole very quickly in Aluminum. Here is a link with a video about how the process works:
http://www.sodablasting.com/
If you are pulling the mast to repaint it rewiring the mast head would be a good project too. It's really only possible to do it right when you have the mast off. The rigging may or may not show signs of problems too. You can also inspect all of that as well as the chain plates. Once you have the mast off an up on stands you can do the work easily. Then as a last step you can prime and paint the mast.