Not too bad - most importantly:
Do a loose one strand running stitch across fabric top to bottom and side to side to find the actual centre, and begin from here. (I told mine now and take a good guess, but have been stitching for years). Beginning in the centre and counting v v v carefully will be crucial to getting it right.
Also, maybe don't do the 'borders' bit first, or the long lines, as if you miscount you won't know until you're trying to squish trees in etc. Try to do a complete area at a time, bar any backstitch / beading (do this last).
Finally - think about whether you're left or right handed when you begin. I've never worked on a floor standing fixed frame before (I like to curl up on the sofa) but I have used hoops LP sized, or roller frames bit bigger than a laptop. With these, I think about when I'll be holding the fabric, dragging my hand across it, where it might get flattened or brushed, and then I begin in the area I can leave alone. For me that's often begin on the right hand side, after I've tracked across a little from the centre starting point.
Good luck! You'll be great.