Welcome aboard Ying!
A chicken will take a lot less time to cook than a pork shoulder.
I suggest you check out the cooking topic page, click here.
Good luck!
I think your piece of shoulder will take about that long give or take... If either is done first, just wrap them in foil and let them start resting while the other finishes. You can put it in an empty cooler, or just put it in the oven/microwave or other insulated place so it will hold the heat (even wrapped in a towel on the counter works well). The good thing with the whole chicken and pork shoulder is that they both have enough fat to make them pretty versat'around orgiving. I had a brisket done and resting an. everyone was running late, so I let it rest in the oven, which was still warm from something else that was just made. The oven was turned off but the residual heat made for a great resting environment.
I'm sure it will turn out great! And of course, welcome aboard!