I'm afraid I can only reply based on my culture's concept of spirituality that may differ to yours in some cases, but here goes;
I'd say no, Sir.
Even for experienced conjurers, there'll always be risks they must be aware of and carefully covered in the process but things can still go wrong easily, let alone for inexperienced people with very limited knowledge.
Simply put, conjuring is something with 'do at your own risk' big red pop up or something.
I am not exagerrating, my master has never done any serious conjuring if it wasn't gravely important (i.e. when a life is at stake), even when he had his share of experience on this spirituality field for almost 50+ years, and has gone through many, many rough and tough things.
Well...he summoned a Kuntilanak once tho, when one of his neighbors boldly said he wanted to get to know a Kuntilanak because they're beautiful in appearance and that he'd do anything to her.
But then the neighbor terrified and ran away upon the sight of the summoned Kuntilanak sitting on his roof during one fateful full moon midnight
My master did it only for fun tho.
Kuntilanak is a bad stuff, actually.
You can if you're aware of their presence and can interract with them, but you don't really have to summon them to come, since they'd usually be the deceased members of your own family that will come from time to time to see how you are doing.
And heaven has it's own way of letting them out to see their living loved ones, to provide them with protection and/or guidance, even when the living one can't actually sense or interract with them.
You can pray for them so they may find peace, Sir.
Do you mean you've ever been possessed, Sir? By a female spirit?
Did she say anything (through your mouth) to your old friend at the time?
Depending on what the spirit that possessed you had to say, we can usually tell whether or not it was a 'gift' so to speak.
Well, you can encounter bad spirits anywhere, not just in the graveyards, if you ask me.
I think 'graveyard' symbolizes a desolate or a quiet place rarely visited by living humans.
Bad spirits that inhabit such places are more dangerous since one of the reasons they stay there is because they don't like/hostile to humans, and their development rarely disturbed by the presence of positive energies any living human carries, so they're usually stronger as well.
Well, all I can say is nobody really knows about the future, Sir. You can pray however, for it. I believe prayers are actually powerful for those who believe.
My advice, Sir? Don't even think about it.
I've seen such websites, and most of them offered the spirit bounding with something they called 'Ifrit'.
Personally, I don't want to have anything to do with Ifrit.
Again, to me it's 'do with your own risk' thing.