You will learn a lot more about Guatemala in particular and Tikal in general if you hire a local guide. The guides are usually found at the Santa Elena (Flores-Tikal) airport, or at the entrance to Tikal National Park, or at the hotels within the park.
Some drivers are also guides, especially for general sightseeing. If you wish to do bird watching, the best known birdwatching guide is Clarence Massiah. He has been guiding at Tikal for several decades. Clarence also guides at all the archaeological sites throughout the Peten. He has been guide for many famous and distinguished travelers over the years. He is well enough known that you can book his services through any major travel agency.
Eventually we will list the guides but as long as you have a local Guatemalan guide who is a member of the guide's organization or a guide for a major travel agency (such as STP or, for the Sayaxche area, Viajes La Montana), you will generally be just fine. Viajes La Montana has two guides who were former IDAEH guards at the ruins, so they know the ruins and the local area inside out. We also have an additional introduction to recommended boatmen for the Rio de la Pasion (and Lake Petex Batun).
For getting to Tayasal ruins across from the island of Flores or for a sunset cruise on Lake Peten Itza all the boatmen seem to be okay.
Drivers are another key item for the success of your visit to Peten. One driver in particular has driven me and/or the F.L.A.A.R. Maya study groups over the years. This is Edil Calderon Granados. He operates Servicios de Microbuses y Taxis "Calderon," and has a booth at the Santa Elena-Flores-Tikal airport. He can take you to Tikal, Yaxha, Seibal (Ceibal), Belice, or Bethel (en route to Yaxchilan).
Sr Calderon can also arrange archaeological guides, hotels, boats for the Rio de la Pasion, Lake Petex Batun (Dos Pilas, Aguateca, Seibal, etc).
You can count on honest and safe sightseeing when you are with a recognized and recommended driver and/or guide.