Within the past month, I have been to both the Sheikh Zayed Grand Mosque in Abu Dhabi and the Sultan Qaboos Grand Mosque in Oman. In both places, I wore long sleeves (to my wrist) and long pants (to my ankles) as well as a headscarf that covered all of my hair. It's not a hardship, and it shows respect. And yes, you do remove shoes before entering the mosques. I walked around in bare feet on gorgeous carpets.