Please be aware that in Dr. Rodger Leir's book "UFO Crash In Brazil" there is a story about a young soldier that held the wounded ET on his lap while being driven to the hospital. If the report is accurate then it is likely that the soldier had direct contact with the blood of the small being. This presumably robust young man with a wife and children reportedly died of overwhelming sepsis a short time after exposure. His driver, another military policeman reportedly suffered no ill effects.
Given this cautionary note, the first thing I would like to do is check to see if the "UFO" saucer showed signs of having been shot down. In the Brazil case mentioned above less than 4 hours after the crash the military reportedly showed up. This suggests that they knew the downed "UFO" craft exact position. Who could have alerted them? One guess is the US military shot the "UFO" saucer down the followed its trajectory by radar during its descent. If this scenario were true the US military presumably could have gotten in touch with Brazilian “friends” and the retrieval operation could have been launched quickly.
Back to the hypothetical problem at hand, so after inspecting the outside of the "UFO" saucer and seeing no "blaster" damage to the hull, if I were in signal range I would take as many pictures as possible and send them via smart phone to everyone I could trust to hold them in confidence. Then with voice recorder documenting my description of the craft, I would proceed to enter to check for signs of life while avoiding touching that might be body secretions. If no "Alien" beings in the "UFO" craft, I would summon help to start a citizens rescue operation with friends I could trust.
As far as the advanced technology goes, one of the many suggestions made by Dr Greer when he trained the initial contact teams in North America 25 years ago was not to seek or accept any technology or take home any devices or materials from the craft. This suggestion I recall was based on the notion that select sections of the national security state in highly compartmented projects were seeking such things. He did not want us to be targeted and harassed by black ops for such technology as he speculated that they would be considered the “crown jewels” to any possible crash and retrieval covert projects.
If there were "Alien" beings present and likely injured I would have to assess the risks in terms of exposure to potentially lethal microbes present in me against them and visa versa. Since I am old approaching my eight-decade of life, no more children to care for and adequate funds for my wife if I were to die before her, then I would do everything possible to save the ET and to hell with precautions.
If "Alien" beings were present but dead, then I would document the scene with a smart phone, send it out on a smart phone ASAP and then say a prayer. I have the hope that if such things as souls exist for ETs and humans and if prayers might help them and us peacefully transition to what ever comes next then, I would offer prayer celebrating the unity of all life in the cosmos.
Or I could just drive by without stopping and say to my lying eyes, “I must be hallucinating because science tell us there is no such thing as "UFOs" flying saucers.”