I want to buy a Yaris, but some questions linger...

[Bluer]

First off; hello everyone! My first post here after reading the threads for a couple of days, and this is clearly a knowledgeable group. So I was hoping you would help me with some concerns I have before buying (probably tomorrow):

I have read that the 2009 Yaris has a CANbus system. Does this mean it will be difficult to add accessories as I wish? e.g., aftermarket cruise control (it is not stock on the model I want) or is it possible, and advisable to have the dealer install one OEM?

Is there any maintenance that ONLY the dealer can perform? I prefer to do my own and have experience (I do my own water pumps, timing belts, clutches, etc.)

What does LB mean please? I see it in some posts...

I want to get window deflectors and mud guards. Is there a certain brand or type that is preferred here?
Do either affect FE?

Thanks for all your help, and I hope to be a new owner this week!
Dave