Let's break this down into steps.
First: Mounting. If you mount on your handlebars with a RAM or similar product you're fine here. No obstacles. If you would like to use the dash mount, there are some obstacles with your dash pad, but they are not insurmountable. Folks have integrated the dash mount with their dash pad and have done most of the homework for you. Just do some searching. It's all posted on here somewhere and pretty well spelled out too.
Second: Power. There is no reason that you can't mount your GPS via RAM and hook it up to a switched power supply (in the headlight loom or tapped to the lighter harness) and have your GPS running without audio in less than 30 minutes. No issues here.
Third: Audio. If you are not seeking the use of the Navigation Interface Module (NIM), but do wish to have some audio for use by your stereo, you will simply need to run the 3.5mm plug from the GPS harness to the input on the front of your stereo. I believe that cord is included in the zumo kit, but would recommend you confirm that for your self. Nothing special here it and would only add a few minutes to your install time unless you get really creative in your routing. There are other more elegant options you can choose here, such as adding an auxilliary (AUX) input to the rear of your stereo, or removing your stereo and shipping it somewhere to have it done. That is not required. As far as the NIM goes, that has been identified as a challenge to install on your particular model. There are threads that explain how to do it in great detail, so I won't go any farther on that subject.
In summary, It sounds like you just want your GPS for basic operations, and maybe use the mp3. Doing that will not be an issue. No special installations. It only gets slightly more complicated if you want to install a dash mount with your dash pad (like they have on the FLHTCUSE5.5 and later). If you want to use the NIM, I would suggest you research a lot and consider the benefits versus the challenges.
BTW, if you get HD RT z660 from a 20% off dealer, it's only about $550 with shipping.