If you haven't played the trumpet at all....
YES, you will need lessons. Ska is based heavily on jazz, and you're not going to be able to play it well enough to play ska within a few months.
Start out with a cheap one from a music store ($600 or so), or (better choice), rent the trumpet. If you still want to do it after a fair time has passed, King is a good trumpet brand. You can anslo look in music catalogs for some blue/red/colors trumpets, too.
Heck, I've been playing sax for almost 6 years now and I only just got bumped up to a top-o-the-line one.