UKPassats

Couple of issues. The spare key fob that I use occasionally appears not to work. Can you change the battery yourself as I took it apart (black frob with fold out key and 2 buttons top and bottom) but I couldnt see anything resembling a battery or is there something else to try first before I go around looking for batteries (ie doesnt recognise keyfob anymor etc)

Also the temp guage now doesnt move at all now sits on the bottom. Any ideas on that one electrical or behind dash or maybe sender ? any idea where sender is its a 1.9 TDI (Red I) S plate.

Cheers