Good luck with finding the correct springs. My 06 broke a front left spring and it was nearly impossible to find the correct spring. Follow Oilhammers advice. Look on the bottom of the spring you will see different paint marks. There are multiple different variations and each of them have a different spring rate. If I recall correctly the TDI is the heaviest variant of the Jetta so there are very few parts that correlate between the gas and diesel editions.
I got lucky and found a set of springs with my matching color code on ebay from a junkyard in Minnesota. If I recall my code was either white, white, pink, pink or reverse of that.
Regardless of how much of a pain it is, do not do like I initially did and try to buy parts from some of the different autoparts chains. It may be more expensive but whatever you can't find or source yourself, it is well worth it to spend the extra money and buy from one of the reputable online dealers or support your local vw mechanic.
These are fantastic cars, but if I have figured out anything, it is that using cheap parts or parts from traditional parts stores usually end up costing you more time and money in the end.
Good luck.