http://www.mitrosmusic.com/proizvod/10393-Ibanez-GSR180-BS/ this one is cool for your budget, about 200 euros, kinda beginner bass but not a bad one :)
Uhm, they will never disable customs. Of course they realise that without CDLCs barely anyone would play the game and actually pay for each official DLC, plus there are only ~700 official DLCs. I don't think you should worry about that. :)
It can't hurt the neck if you take off all the strings at the same time, clean the guitar and then put the new strings on. It can't take more than an hour, so not much can happen. :D source: been doing it that way for the past six years, nothing bad ever happened :D