306 help needed...

[lucky_me]

My elderly father has a 1997 Peugeot 306 which he has owned for 4 years and loves dearly. However the mechanic he uses has suggested he sell this car as it has developed a transmission leak from the base of the kick-down linkage. He has some other issues with his pug, but this is the main focus of concern. I'm no mechanic myself, but this recommendation seems extreme IMO and is causing my father some consternation.
So I just wanted to throw this open for comments and advice... Is this a common problem or an oversight in servicing, or just one of those things?
His other issues are;
1. A yellow/orange lead under the passenger seat that's disconnected.
2. A blue sensor near the coolant fill point region without a lead (perhaps part of air-conditioning?)
3. The air intake has an outlet off to the side that has been plugged and taped up (perhaps a hot air sensor missing?)
4. A loose connector (purple) that may have to do with point 3 above?

I appreciate any help or advice you may be able to provide to sort out these issues as I really would like to see my father keep his 306 as it has otherwise been a great and most suitable car for him.
cheers