New to LED so I need all the help I can get.

Ok. First off im very to to LEDs. However im not new to electronics and sodering.

My project is this. I am making puddle lights for my truck. There are many options that I can go with, but i decided im gonna use LEDs pointing in a direction mounted under the truck body and powered by the interior light in the fuse box which is 12 volts.

OK that said. Here is my design, Im gonna mount the LEDs inside of a PVC pipe cut in half. That Way I have have the LEDs in any direction I want. From what I read I can do parrell connections to make it work. here is what im following to make the string of LEDs http://www.instructables.com/id/E0IF0SU7NAEP286VHV/

ok now that I have all that out of the way. Here are my questions.

what do I need to do to get 100 3.5v LEDS working off 12v power source. do I need to put a resister on each of the LEDS or can I just put a resister on the end of the positive? Its all still new. Any help would be apreciated. THanks

Here's a page that calculates resistor values for arrays of LEDs: http://led.linear1.org/led.wiz

Little 5mm LEDs are really not too bright if there are streetlights and such around, but you can make up for it with sheer quantity (remember such lights have to reflect off the ground which is frequently black asphalt). Luxeon LEDs would be far brighter (brighter even than real neon tubes) but need heatsinking for maximum output and life, so epoxying them directly to the steel frame would be better than insulating them in PVC.

Aluminum or copper would be better, but steel isn't too bad compared to PVC. And there's little need to fully waterproof such low-voltage circuits.

Welcome and good luck!