Interior Painting!

[HotDonnaTheBus]

Hi all!
I just bought a beautiful 2001 Ford E350 short bus. It's been my dream to convert a vehicle and live in it for many many years now, so I'm excited!
I know most of what I'm doing, in general, but just looking for some sage advice on how to paint the interiors? Everything but the ceiling will have wood-paneling, so I'm trying to paint the steel a nice color.
Should I sand it first? Or do I just need to prime it? Can I get by with spray paint and/or a roller instead of buying a spray-gun?
I'm a college student on a budget, so trying to do this as cheaply as I can while also doing it right!

Thanks!

[Tango]

Any original paint will need to be either sanded, scuffed or chemically prepped (See "Liquid Sandpaper") in order to achieve decent adhesion.

[Johnny Mullet]

Welcome aboard. I lightly sanded my ceiling and then the paint would stick good. If it's shiny, it won't stick.