A shay is not an inexpensive engine. So I doubt it is DC only. The AC will run most of Lionel. Unless you go with any unconventional operating systems. Mike found the good manual it does have sound buttons so the extra sound activation buttons are not needed.
The best thing is to find the model items and research them at Lionel to get the information. The shay must have a model number and a manual, The box would have basic engine information.
Basic questions are. AC or DC motor, electronic, two or three position reverse. Then you have sound and control boards.
Many engines have DC motors that run on AC with electronic reverse units.