Will instructions be included with the purchase of the part?
Not usually no. The only time instructions are usually included with appliance parts would be if there were changes necessary (eg. to the wiring, etc.) for the replacement and it would only describe those specific changes, not the whole repair job.
The following service manual might help with the basic construction of the appliance:
LINK > Electric Slide-in Chassis Range Service Manual
Is it relatively straightforward to install.
Once you have access to the original control, swapping the replacement shouldn't usually be difficult.
The Appliance Information Site