Some of it will also depend on exactly what welder you have. If you can't get the parts you can't convert it. If it's a lincoln I'd call them. They can tell you exactly what part(s) you need.
The wire welders usually want certain wire sizes. AL wire tends to be pretty thick. you have to make sure the drive rollers and feed tube can pass it properly.
When you change gases you may also need to change the regulator. At the least you'll likely need to change the fitting. Diferant gasses often have diferant fittings and may require diferant regulators because of diferances in cylinder pressure and the fact some gasses don't like the materials some regulators are made from.