confirmation on how to interpret MCMCglmm summary output

i want to know if post.mean is similar with estimate result that we see in glm model or different? thus pMCMC can be consider as p-value? i have not found people really explain on summary analysis usually they focus on something else.

lastly, how to set prior and how i can be sure that my prior is correct? here link i have read but still cannot understand. http://www.wildanimalmodels.org/tiki-download_wiki_attachment.php?attId=24https://cran.r-project.org/web/packages/MCMCglmm/vignettes/CourseNotes.pdf this my result that i obtain.

 Thinning interval  = 10
 Sample size  = 1000 

 DIC: 0.3723323 

 G-structure:  ~time

     post.mean  l-95% CI u-95% CI eff.samp
time     11189 4.032e-17    13211     1000

 R-structure:  ~units

      post.mean l-95% CI u-95% CI eff.samp
units    308299    24934   815369     68.1

 Location effects: sleeve ~ pain + stiff + diff 

            post.mean l-95% CI u-95% CI eff.samp pMCMC
(Intercept)    72.812 -334.677  433.864    467.2 0.550
pain          -33.016 -156.926   68.739    451.5 0.522
stiff           1.016  -95.617   88.061    479.0 0.984
diff            1.799  -25.380   25.683    772.7 0.902```