I-485 filed EAD card received. Can I get another part-time job?

[wind8868]

I work full-time for a company under an H-1B visa. I have filed an I-485 and received my EAD card already. In the meantime I'm doing another graduate degree at a university. A professor that I like is looking for a research assistant. I expressed my interest and he seems to like me too. How could I take this part-time RA job? Does the school have to get a part-time H-1B visa for me? I'm afraid they won't do it since the application fee is pretty high. I heard that I can use my EAD card to work part-time on another job, but it's said that this means I'm giving up my H-1B status and thus it's quite risky if my green card does not get approved before my EAD card expires. Any advice will be high appreciated!

Victor