Painting - Paint old ceiling tiles?

I purchased a house with 12 inch tongue and groove ceiling tiles applied over a plaster on slat ceiling . I imagine the tiles are about 40 years old. I would like to spackle the grooves, seal the tiles and apply a textured wallpaper (ceiling paper?) to the tiles. Is this a good idea? Any suggestions. I do not want to take the time or money to remove the tiles and plaster.

It should work, but expect 2 and maybe more coats of joint compound (not spackle) to fill the grooves. Also be forewarned, I have come across and had problems with tongue and groove applications where they are not solid. Meaning the tongue n groove part allows them to move around slighly, making it very hard to skim the grooves, as they keep moving around. A heavy-duty liner such as a non-woven or plaster impregnated flexi-wall system would work too. Good luck.