Otto, I've never tried to refinish a laminate stock, but if I was going to try it I'd probably use Trans-Tint concentrated dye in Dark Walnut. You can order it from Rockler or Woodcraft, and you can mix it with water or alcohol to whatever strength you want. I've used it with water and with alcohol and I prefer the use with water (distilled water). After all the sanding and grain raising/dewhiskering is done, apply the stain to get the darkness you want, and once the wood is dry, then you can apply the finish. If you are going to use a varnish, you don't need the wood sanded any finer than 220 grit. If you're going to use the Boiled Linseed Oil, I'd sand and grain-raise to 400 grit before I applied the stain. I do wonder how well a laminate stock will accept stain evenly. I'm thinking that the various layers of wood will probably each accept stain differently. Maybe someone else on the forum has experience with that.
Mix the stain with the distilled water and try it out on small hidden spot on the stock so that you can find the darkness you want.
And the OP's stock, which looks fine, could be smoother and shinier if he wet-sanded (with Linseed Oil) to finer grits like 320 and then 400 and then maybe 600 if that's what he wants. That'll put a paste of fine dust and oil into the wood pores and smooth out the appearance of the wood. Hand rubbing daily after that will add more shine. An old book I have (from the 1930's) suggests that hand rubbing should be done daily for no less than 90 days for best appearance. And back in the day they'd use real sharkskin and Rottenstone and oil to fill the pores prior to getting to the hand rubbing part. Personally, I've never gone to those extremes, though I have considered it (not the sharkskin). If I had just the right walnut stock, I'd probably have a go. I wouldn't work that hard on mediocre walnut.