I'm thinking of giving the 4Runner a break and get a daily driver. I'm thinking of getting a Jetta TDI, but worried about reliability of VWs.

I've seen mostly 2004 Jetta TDI for sale which makes me think there might be problems with this year.

Does anyone know which year I should avoid? Or if they have issue like the 4Runner headgaskets....I've tried searching Jetta Forums but this question doesnt seem to get any replies.

TDIclub.com is where you wanna be. Stay away from the Autos. they are turds.
Make sure you use the correct oil, and change your timing belts at the required intervals.

I used to have a 02 jetta tdi. If you are looking for that body style (4th generation) 99-04.5. Avoid 99 and 00. they were still working out some kinks. 03-04.5 has a different motor (PD) than 99-02 (ALH). Body are good motors, but the newer ones have better upgrades than the older. The autos are not very good. The manual trannys are great and you can swap in a 6 spd. The biggest thing is to make sure it has been maintained well and the timing belt was done correctly.

I have a 2000 jetta TDI 5 speed. 176000 miles. I have owned 3 TDI's. Stay away from auto's. Make sure you have documented T-belt service. If not plan on having done when you buy it. Intakes can carbon up. But I love no less than 36MPG- As good as 55MPG on highway. I also use some sort of diesel fuel treatment quite often (staydyne?) Glowplug relay issues-always. But I live in Florida so I don't care. I also had to reseal the injection pump-so check and make sure that is good. My Favorite so far was a 1997 Passat TDI 5 speed.- had it to about 250,000 before I sold it... I still miss it.

Yep.

My 01 5 speed gets no less than 43, and over 50 on a road trip. 750 ish mile range on a tank, and I carry a 1 gallon can of diesel spare JUST IN CASE....

Last summer we took road trip to PA. Averaged 45mpg! Crammed family of 5 and all our stuff in it!

I have a 2009 Jetta Sportwagen TDI and I love it. The 2004 was a good year. The trouble year was 2006 because the engine does not lubricate properly.

The best year in My opinion was the 2009-10 because they have the 5 point racing rear end, the interior is much higher quality than the 2012, they have the 160hp 2.0 tdi and they have the DSG transmission which is a great tranny. I have a 6speed but the DSG auto is great.

Do they have any AWD TDI models?

The New England winters are why I drive an Audi with AWD and snow tires.

Nope, unless you get a touraeg... jetta / golf / passat / audi A3 TDI's are all fwd. FWD decent with snow tires in winter... awd wont get you much farther... it's all about ground clearance....

No but a good set of winter tires and LOW grunt of the the TDI Plus the engine weight- they do pretty good.