List of questions about Trafic Generation

[Tragen07]

Hello!
A few days ago I bought a Trafic Generation 2007, 2.5l quickshift. The van is in ok conditions but there are several things to fix. I like to work on it myself so I'll use the forum a lot to find the info. As the model has been out for several years I bet a lot has been written on it already!

As I don't speak spanish very well and for sure I do not know the technical words, I thought I could list here the issues and questions and maybe somebody kind enough could point me to the right direction ( instead of opening a new thread for each of them).
Hope it works!

1: One parking sensor doesn't work and lately I get the continuous beeping as soon as I select the reverse. Is this a common issue? Any likely culprit I can look for?

2: I get a gearbox warning light sometimes. Sometimes it goes off. Should I be worried or I can keep driving?

3: Rear windshield defogging doesn't work. I replaced the fuse but still nothing. Is there any specific point I should focus on?

4: My van doesn't have auxiliary heating although Renault had some versions with it. I would like to install a webasto and fit a second battery and would like to keep the installation as "original" as possible. Do you know where I can find info about the original layout? Where the webasto is placed? Wiring? etc

Can't wait to start playing and tinkering with the Trafic!!! Thanks a lot for the help!