Hi, i work for an ISP and am a home user so i can hopefully answer your questions.
If you're on some sort of DSL line (ADSL/SDSL/VDSL) you can connect your new router/modem to the incoming line.
If youre on fibre/NBN you will likely be able to do the same thing. The only time you will may be restricted by your ISP as to what modem you can use is if you're a business customer. If thats the case, look into Mac Address spoofing for your particular model.
You just need your internet connection details (PPPoE email/password). You should have these in an email from your ISP, if not you can ring them and get them.
Let me know if you have any further questions.