Hello, This may seem like a really noob question, but can a Skink Priest join a unit of Saurus Warriors? I do have a rule book, and I assume this would be a legal move... but hey I'm new to this and want to make sure.
Yes, he can. You cannot put him rank and file in the unit as his base size is not correct. You would put him to either side of the unit. The only downside is that his movement becomes 4 while he is in the unit.
Plus he's in a close-combat unit, whilst the Skink Priest is dead meat up close. Better option is to take the Cloak of Feathers to zoom him around where needed (remember, you can channel those nasty short-range spells from Lore of Shadow/Life/Metal through him), or take him on an EOTG. Saurus don't really need attached characters to babysit them anyway. Keep them nearby the Slann+TG block, buff accordingly, they should do fine. They're mostly there to chew up weaker infantry, intercept charges meant for the TG (thus giving you time to reposition/use magic hax from the frog to annhilate the threat), and protect the flanks of the TG.