If you cannot find the manual immediately, here are the standard specs for the Nissan E13 engine to get you started:
Standard GAP is typically 0.8mm to 1.1mm depending on the specific ignition system. Oil Grade: 10W-30 or 20W-50 depending on the climate. Manuals & Resources: Haynes Workshop Manual nissan e13 engine service manual
Do not rely on generic advice. Do not trust "that one YouTube video." Spend the $20 on a 24-hour Nissan TechInfo subscription, download the PDF, and keep it on your tablet in the garage. Your E13 will reward you with 200,000+ miles of trouble-free driving. If you cannot find the manual immediately, here