Skipper Conor Hourihane and Paris Cowan-Hall put Argyle into a commanding position before substitute Ryan Williams reduced the arrears for the Shrimps, who saw Andrew Parrish sent off late on.
Victory moved Plymouth out of League Two's drop zone, and Sheridan said: "The most important thing was getting the three points. We rode our luck at times but all that mattered was getting the win.
"We got off to a flying start with two great goals but when we were 2-0 up we needed to show a bit more nous.
"It's early days yet, though, and they area young side. I am going to have to teach them how to build on a lead.
"The most important thing is the three points. I am really pleased with the players because their attitude here and in training has been different class.
"Obviously the two goals coming so early did us a big favour and gave us a cushion. We got a bit edgy late on but that's natural in our position, it's not been very often they have had a two-goal lead to defend."