I don't know how strong your mushrooms are but according to what I read above and the value/quantity of the deal you've made, it should be a mild to medium dosage. Normally your dealer should know and tell you something about it if you ask. Have you asked him ?
Good stuff to do on a first trip ? Well you want to take mushrooms because you want to know what it does I guess. So that's what your first trip is going to be about. No need to plan stuff to do. The experience is usually rich and interesting enough to keep you busy for the duration of the trip.
If you are preoccupied by losing your mp3 player, then don't take it with you as 1) this preoccupation may affect the quality of your trip or 2) you may lose it because you won't care about it at all anymore so much that you are going to throw it away if it annoys you for some reason, lol.
If you go through a phase of anxiety before the full effects manifest, don't worry, chill out, it is not going to last. After that, natural fears you have, especially irrational ones, might manifest and be greatly amplified, this is what's called a bad trip. It does not happen if the setting if good. Eventually you might feel glued to a time spot and freak out you are going to stay at that place and time forever. If so chill out, it ain't going to happen.
Other than that you may be scared only on extreme doses really and it revolves around the fear of losing identity or sanity or even life but in my experience (I lost the three of them in a row) this stuff can only eventually happen when the trip has become totally internal and awarenes of one's physical surrounding is totally lost so there is no whisky bottle at hand anymore. Some brief moments of pure existential terror and extreme mental pain.
The best in those states is to accept what appears to happen and not fight against it. The more you fight the more you are terrified, the more you experience mental pain. I am saying that in the case you would be hypersensitive to mushrooms.
When I first took mushrooms (a medium dose), the settings were really not optimal but the interest of the experience itself obliterated whatever bad vibes should have normally affected me. A thouroughly enjoyable and smooth trip from begin to end.
Which is what I wish you also.