Can I explore Petra myself after the 2 hours or should I pay extra for tour guide?

In Petra you just need to follow the path, and they have explanation signs on each place you reach, you will be given a sitemap with the ticket at Petra  visitor center, and each spot on Petra has explaining signs with 3 major languages. A local site tour guide along Petra (for site detailed information) can be requested if desired.

Local tour guides can be requested and arranged in Petra Visitor center if not included at your itinerary, and it will cost 50 JD (around 70$) for basic trail coverage - around 2-3 hours.