If you provide your VIN, someone here with access to ServiceBox (Peugeot and Citroen's servicing and maintenance information website) will be able to look it up and tell you exactly what flavour of 406 yours is (it will usually be steve_earwig who does this for you
)
Since yours is an X-reg car, it will be a phase 2 (face-lifted) model (you'll see this referred to as a D9 here as this was Peugeot's design number for the mk.2 406). The front of the car will feature a honeycomb grill on either side of the heraldic lion badge, and you will have chrome strips along the cheatlines on the sides of the car.
Being a D9, your diesel engine will be an HDi, which come in 3 main varieties - 2.0l 90 BHP, 2.0l 110 BHP, and 2.2l 140 BHP. The 110 and 140 BHP models feature intercoolers, and the 140 BHP model will have both a dual-mass flywheel and diesel particulate filter.
Welcome along, hope you get your niggling issues sorted out and enjoy many miles of comfortable motorway cruising
, 
