Expert advice needed!!!

[punarhero]

Hi everyone,
Our team got a project to build a robot for a museum as a fundraising project. Basically there are pictures on the walls around a rectangular room. First of all, the robot is supposed to recognize is a person is within 5-10 feet of it, and greet it (with an audio recording). Next, it is supposed to go around the room, stop at each picture, and explain a little about it (again, pre-recorded audio tracks). After going around the room, it is then supposed to come back to its original position. Oh, and by the way, I am planning to use the EDU robot controller for this.
There are a few things that I would like to get expert opinions on.
1) The robot has to be able to recognize a person within 5-10 ft. of it. What can I use to do that. If there is a product I can buy, I'll appreciate if you can tell me which company makes it or from where I can buy it.
2) The robot has to stay abt. 10 ft. from the wall. What is the BEST way of navigation. The avg. speed of this robot will be abt 4 ft./sec. I could do line folowing, but rather not. This robot has to run abt. 10 hrs. a day, 5 days a week. What can I use for navigation which will minimize error, and to make the robot go and stop right next to the picture every time?
3) The robot has to have about 20 different audio recordings on it, all of which need to be easy to re-record. I could use an MP3 player, and have a mechanism hit the NEXT button every time we need to change the track, but that is not very reliable. Can anyone suggest something that is more electrical than mechanical, and that can be controlled with the EDU controller.

We have to make this robot in about 3-4 weeks. I'll really appreciate if you can give me details on how to solve any of the three problems we have to solve for this robot.

Thanks,