Hi there,
I wish you all the best in this new direction. I'm a long shot from a professional, and haven't used much java, and no Perl (except in the form of Template Toolkit) or LAMP. I've tinkered with web design and done some graphics manipulation along those lines though, so since noone else has responded I'll put in my humble 2 cents. I've used Dreamweaver MX but never Photoshop. I use GIMP instead. You might be interested in a glimpse through this article:
HTML Editors in Linux - A Comparison
However, the article is possibly a couple of years old. For instance, Quanta is listed as version 1.0, and is now 3.3. Bluefish is listed as 0.6, but is now at 0.13, so I don't know what's up with that. Here's
Bluefish's website. I haven't yet used these programs yet with Linux, so sorry but I have to just offer that info for what it's worth.
I have used the GIMP a fair amount in its Windows port over the last 1+ year, and can say it is a high-quality program. It doesn't have as many plug-ins as Photoshop, but you can produce high-quality images with it. There are online tutorials, you just have to look around.
You also might consider looking into learning a version control system for when you work on projects with other programmers. Open source is definitely CVS, although you might not be able to use that if working with Windows folks, since CVS is only ported to Windows and not "native."
You might consider finding some webmaster forums and reading the documents and advice they provide there. I'd bet you'll find some handy although of course biased info.
Sorry I can't be more useful.