I'm sure it's pretty easy to install because most php mysql scripts are. I didn't think ipb was still offering a free version,... probaly just using an older one. Either way i'm sure you'll be able to install it fairly easy because it should come with step by step instuctions, especially if you bought it.
You have to pay for the full version of IPB 2 (theres is a demo). IPB 1.3 is free but you can´t share it with anyone and can only be distrobuted through fantastico or ipb free.