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Yes, that should be easily "doable" with Inkscape.
Before I get too involved with suggestions/instructions, I have a couple of questions. Oh, and before I even ask questions, you might want to learn about the difference between raster (paint programs) and vector graphics. It's something I still have a hard time really understanding from the technical perspective, but it results in some quite unexpected problems, if you haven't realized how very differently some things are done with vector vs raster. Here's the Wikipedia article on Vector Graphics, as a starting place.
So questions

Do you want actually the image of a tree to lie behind the text? If so, an existing image, or one that you want to draw? Or will it be only text that is deformed in a tree shape? If text only, do you want some texture applied to the text to give the appearance of bark and leaves?
Well at least I think I could get you started with the "ARB"/trunk.
1 - Using the Text tool

, type the letters.
2 - Next look along the top of the canvas, just above the ruler, to see the tool control bar (this will change for each tool used). There you can select the font that you want, and the size of the text (and several other settings that you
probably won't need).
3 - If you can't find a font (there are many free ones to be found on the internet) that will give you the proper proportions for the tree trunk, it will be easy to adjust it manually. Select the text with the Selection tool

. You can drag those arrows to make the text larger, smaller, wider, taller, shorter, etc. (If you want some curves to the trunk, I'm thinking the Tweak tool

will work, but let's see how it goes, and what develops, since I haven't seen the sketch yet.)
4 - Once you have it like you want, you should probably convert it from Text to Path (because usually a printer will want it that way). This is done from the Path menu > Object to Path. But note that after you do that, you will no longer be able to use the Text tool to edit it. Now you will only be able to edit with the Node too (or still the Selection tool). Since this is not a reversible step (except via Undo) I would suggest saving a copy of the original text (it can later be hidden or deleted, when you're sure you don't need it anymore). It's kind of handy to just drag it outside the image border (which is the rectangle that's showing when you first open Inkscape) while you work.
So give that a try! I realize there will be many "what ifs" and "how did that happen" once you get started, and we'll be glad to help with those -- one step at a time, as they come up

Also, if you can produce a sketch that is pretty close to what you want, you might instead scan it into your hard drive, and import it to Inkscape. Once there, you could trace it manually with the Pen

, Pencil

, or maybe even Calligraphy

tools. (Although the Calligraphy tool may be a bit difficult for a beginner, it sounds like you already have some skills, and perhaps could pick it up quickly?)
Or else an alternative to tracing manually would be to use Path menu > Trace Bitmap. This automatically converts whatever raster format you assigned it when you scanned it (usually BMP) to vector. Then you could simply use Inkscape to color it! Whether manual tracing or using Trace Bitmap would be best, depends on your sketch and your goals. (If you need a centerline trace, Inkscape's tool can't do that, but there's another one on the internet that can. But as I said, one step at a time, lol!)
Yes, a screenshot of your sketch would be so very helpful to us, to offer suggestions

Also, if you haven't already found it, Help menu > Inkscape Manual (requires internet connection) will probably have instructions for everything you want to do in this project, unless you need something really fancy (like a custom filter, for example). Plus, Help menu > Tutorials are all very well written for beginners (even the one titled "Advanced", lol!). (I know you've said that you've already looked at some tuts, but if it's the middle of the night and the forum's quiet

they're a godsend.)
I actually have a degree in forestry, and worked in urban forestry/arboriculture for several years. I'm not sure about everyone, but I think many people who work in that field fantasize about starting our own business. So I'll be interested to see your sketch. (My fantasy logo was gonna have a ladybug in it

. Well, that's not the image I drew, it was before I had a PC. This is me now, lol

)