I need to know if trying to talk with this individual on my own has immediate negative legal consequences. It does not help if I'm saving hypothetical dollars that I won't ever end up getting because I spent my budget on legal so I didn't have enough to finish my latest game.
It is not an absolute. What you communicate with them CAN potentially have serious negative consequences for you. It also CAN get you the results you want.
It depends on exactly what you say and how you communicate it.
If you communicate it clearly about what you want, and what you write about is proper, and you show good faith, and do not make legal threats, and follow the law, then you will probably be fine.
If you do not communicate clearly about what you want them to do, or what you write about is even potentially improper, or if your words can be twisted to show you do not show good faith, or if you even hint about making legal threats, or if approach the borderlines of being afoul of any part of a very complex set of law, then you could create very negative legal consequences.
The steps are simple enough assuming you went through the proper channels to set up your company. Use a printed corporate letterhead if you have it. State that you are a business incorporated in <<location>>, that you have been using your mark in business and have been registered with that state since <<year>>. Then state that you just noticed that the other group is using your name. Politely tell them that you believe them to be infringing on your trademarks and that you want to discuss the matter with them.
A small list of things you shouldn't do include: During your first letter, do not offer any solutions, simply state that you want to talk. Do not threaten, or even hint about the possibility of threats. Do not mention anything about payment or repayment or any dollar or value amount. Do not use any language that conveys frustration or anger. Do not state it as a demand. Do not use "legalese" or attempt to sound like a lawyer. Do not impersonate a lawyer.
Unfortunately, as a non-lawyer it is very easy to step on a legal landmine. There is a long list of keywords and phrases that you need to avoid. Mess up and it could backfire, landing YOU as the defendant. Anything you write could be used against you in court, and it could be used against you on the Internet in a smear campaign against you or your business.
The trick is that you want something that requires action on their part, so a polite non-threatening letter may not get you the results you want. Or it might get you exactly the results you want.
Just know that if anything goes badly, the $150 or $200 you could have invested in a lawyer up front may grow to a $15000 or $20000 legal bill if it backfires. You may be saving a little money now, but it is a gamble most companies find foolish and unnecessarily risky.