My experience, from many years doing my business in men's restrooms, is that guys pay very little attention to one another in men's rooms. For one thing, if you're too interested in somebody else, they'll think you're cruising them.
I think the worst that could happen to you in a men's room would be that a man would think you're an effeminate man. They're not going to bust you for being a woman in a men's room -- most men wouldn't mind that at all! So square your shoulders, wash your hands, and don't make eye contact, and you'll be fine.
Oh, and don't feel self-conscious about using the stall instead of the urinal. At least 10% of men have trouble urinating when other men are nearby. Lots of us use the stalls, just for reasons of privacy and lower tension.
*** Jenna ***