Ok, I'll try my best to get you your answers.
Keyless go, KESSY, is only on the SEL Premium trim lines. I have it, and every now and then it's iffy in my pocket. Maybe my pockets are too thick. But when I have it in my hand it works maybe 95% of the time. The other 5% usually just requires me to back up, wait a few seconds and try again. The sensors for KESSY ONLY work when you're near the car. For example, you no one can open it if the key is in your house. There is no keyhole in the steering column but their are hidden door locks that are plated off on the outside handles. If your fob battery dies, and the car can not read it, you can put it up to the plate on the steering column and it will sense it and allow you to start the car. And the door keyholes are for locking/arming and unlocking/disarming.
This is the range here.
No SEL's come in manual. Only 2.5L S/SE (both base) and TDI SE (also base). Which means no manual and any options (sunroof, nav, premium audio).
Fender, in my opinion, is great! They worked with Panasonic and they did a good job. But that is also only on SEL trims and I think 3.6 SE with sun/nav trims. The only unit that is sluggish is the RNS-510, which is the high end unit in SEL trims. The other units, though having different issues, respond a lot better.
The three engines basically have their own strengths. The 2.5L is a simple, proven tough engine, and with a standard auto, won't have that dreaded 40K DSG service. The TDI is for economy, mainly highway but city is not bad either. And the 3.6 is power, pure and simple. The downsides are, the 2.5L only gets okay mileage. The TDI doesn't have a lot of high end passing power. And the 3.6 is expensive in comparison and takes the most gas.
I can't comment on the TDI maintenance, since I've never owned one. I"m sure someone else here can help out.