1) Yes, dual band (2m/440) is a good thing to have, especially in CA where 2m is crowded. Outside CA 440 isn't as common but it's still good to have. Most 2m/440 radios can also be "opened up" to allow them to transmit out of the ham bands on things like FRS (462mhz). My frs and cb radios in the jeep are actually a 2m/440 radio and my HF radio.
2) The features you need in a radio (transmit bands, output power, memories, etc) are important but installation is just as important. Most mobile ham gear will have a removable faceplate so you can install the radio body under the seat and only have the control head where you want it. Some radios have the heads permanently detached so you have to do this. You will also find radios with the mic connector on the control head, on the radio body, or both and this can make a big difference in installs. My biggest criteria in choosing a radio is how easy is it to operate with my eyes closed. I can do almost all of the normal tasks (memory changes, squelch, volume, transmit power, lock unlock) without having to look at the radio, so I can do them while driving.
3) The ft-8800r is a very good radio, I have one in my niner, a buddy has one in his tacoma 4x4. It is a good solid radio with all the features you need and some nice ones as well. Things I don't like about it are the tiny hard to read display, only having a mic connector on the control head, and the mic is poorly laid out and doesn't lock well. For those reasons I prefer the icom 2720 I have in the green pig. The display and controls are much nicer and easier to work with, there is a mic connector on the body of the radio that I have run to a connector in the center console, and the mic itself is nicer. Unfortunately the 2720 isn't made anymore and the replacement (2820) which we installed in the cooper isn't as nice IMO. You can still find the 2720 used, we just installed one in my shop managers 2014 diesel grand cherokee.
Before buying a radio I suggest playing with one in person to get a feel for the controls. You can mess around with the demonstration models at HRO http://www.hamradio.com/, they have stores in oakland and sunnyvale.
I have programming software and the cables for most yaesu radios and older icoms like the 2720.

