This internship will most certainly be positive for you! This experience will be of more value to you than many other things you could do during your summer. Maybe also find time to volunteer.
My background: I got accepted to an engineering internship at Boeing in 2005. I later took a job there and have been here over 5yrs now but spent half that time finishing my pre-reqs while working, they were so kind as to pay for all my classes and books! I am starting med school this fall actually (yep, changed my status to med student prematurely). It is my opinion that some degree of professional work experience (i.e. working in a team solving problems with deadlines) is something that an admissions person might look highly upon. And engineering at GM is just fine, company woes are due to higher management!
A man in a hot air balloon realized he was lost. He reduced altitude and spotted a man below. He descended a bit more and shouted, "Excuse me, can you help me? I promised a friend I would meet him half an hour ago, but I don't know where I am."
The man below replied, "You are in a hot air balloon hovering approximately 30 feet about the ground. You are between 42 and 44 degrees north latitude and between 83 and 85 degrees west longitude."
"You must be an engineer," said the balloonist.
"I am," replied the man, "but how did you know?"
"Well," answered the balloonist, "everything you told me is technically correct, but I have no idea what to make of your information, and the fact is I am still lost."
The man below responded, "You must be a manager."
"I am," replied the balloonist, "how did you know?"
"Well," said the man, "you don't know where you are or where you are going. You made a promise which you have no idea how to keep, and you expect me to solve your problem. The fact is you are exactly in the same position you were in before we met, but now, somehow, it's my fault."