First project help -- Motion Sensor burglar alarm w/ text alert.

I think someone has been casing my place lately. If like to make something that I can mount outside my side door (maybe facing downwards since it'll be under an awning) and have it send a text message if it senses movement. And maybe have it play a noise and shine a bright led to deter thieves.

I found a project (another similar one) that is pretty much just what I need, but (even with the what you need list) I'm a little unsure of what I would really need to make this work for me.

I don't like the plastic bowl as a case look for it at all. Also, keeping in mind I'm new to Arduino projects, I notice there are multiple types of boards available for purchase. Is the UNO rev 3 all I would need? And in terms of a case, are the generic plastic ones I see on Amazon durable enough to be outside and accommodate the motion sensor and whatever else I need to attach. Are these things inevitably going to be hanging or glued down or?

This made sound stupid, but i just want to make sure when I get ready to purchase everything I get exactly what I need.

Also, if anyone has a better take on this project (reasonable in complexity and price) id appreciate it.

The project mentioned above:

You need some kind of Arduino, then you need something to send texts.

It's unclear how he does it. You don't need an expensive board though.

In order to send text messages, you need a GSM shield and a working SIM card. you can configure everything from your Arduino sketch.