A newsletter created with InDesign would really look like top notch top shelf top of the bill one (uh, perhaps I'm mixing up metaphors here) -- but only when created by a skilled InDesign user. InDesign is used by top graphics designers all over the world.
In the hands of a beginner, it's more cumbersome than, say, Word (which will do a /decent/ and very easy job) or MS Publisher (Windows) or Pages (Mac) to create a *fairly basic* newsletter with.
InDesign, with all of its extensive control over typography, text, layout, and press-ready output, is not really targeted at the Goodwilling Amateur end of the market.
However, the 30-day trial can be freely downloaded, and the Online Help will at the very least get you started with Creating Your First Document.
What Jongware said, also I note you say "bringing in-house" which indicates you get it done already and have a standard to keep to. If you can post that online we can tell you whether it's possible to use something else or whether you will need a tool like InDesign to produce it.
If you're willing to learn InDesign can definitely do it, another option for learning is lynda.com.
InDesign is great, but perhaps difficult to learn; however I taught it to
myself and that was hair-raising, and if you can find a teacher, it's
probably easier. I use it to write user manuals, as I find it extremely
reliable, though more work-intensive than Word; I'm sure your company will
be able to use it for much more than just newsletters, should you purchase
Don't count on the online help too much, as it's difficult to understand
and not beginner-friendly. If you can't find a course, find a designer to
come in and teach what they know.
IMO the best thing to do would be to sign up for Adobe forums; I don't know
whether you can do that if you have a trial version, but you can do it once
you buy the program. Post your situation, and even post your work, and
many fellow members will spring forward to give you all kinds of advice.
You can use these forums without even having InDesign! Although that would be sort of pointless....
Oh SORRY...I'd thought the mail came from a different list I'm on, lol!
If you go ahead and use InDesign for the newsletters one advantage is you then have the skills in-house, allowing you to create other materials in the future (brochures, adverts, marketing pdfs etc.) which a more basic package may not give you.
In terms of training I can see that Adobe has an authorised training partner (AATC) in Sacramento (AcademyX Computer Training, 180 Promenade Circle, Suite 110, Sacramento - Phone: 916-333-5710 - http://www.academyx.com/schedule/sacramento/ ) and there are a number of others throughout California but not specifically in Sacramento. As a UK based AATC, I can't really tell you much about these guys, but I can tell you the standard with an AATC is generally going to be high as the courses should all be delivered by Adobe Certified Instructors who will be Adobe Certified Experts in InDesign.
Hope this helps.
I recommend you hire a professional designer to create the newsletter for you. At least it will look neater and more professional.
I also recommend that if you want to keep updating the newsletter yourself, that you firstly explain that to the designer so they can talk to you about handing over the source files (different contract than just design).
You should buy yourself some books, Sandy Cohen's Quick Start Visual Guide is pretty good for a beginner.
I also recommend you do tutorials on tv.adobe.com and also on Lynda.com.
But updating the text is only half the battle. You will need to find graphics suitable. Perhaps buy a Collection of images from a Stock website, either CDs or online purchase (whichever suits).
You can't just go pulling images from other websites, google or other image search engines, you will need to consider that images are copyrighted, hence buying stock images to use in the newsletter - where you can.
And then you will also of course need image manipulation software, as well as Indesing. You will need Photoshop to edit photos and Illustrator for vector graphics.
Of course you will need to learn these programs too.
Then of course you will need to know the difference for Print and Web. What caveats are involved in both.