Just a note on soldering tools for this.
Soldering leads to a 603 or 804-sized surface-mount component is nearly impossible with any kind of "standard" soldering iron. On Peteski's advice, I invested in a Pace ST50 digitally-controlled soldering station with a TD100 iron. The TD100 is nearly as small as a real pencil (well, actually, more like a good hefty fountain pen, like a Montblanc President, which I'll never own, but have touched on occasion); the tips are interchangeable (and the tips contain the actual heat cartridge), but I've found that the 1/64" conical tip is perfect for 603/804 sized components (and they are pretty cheap - about $12 each). The key here is that you can set the temperature of the ST50 precisely; the tip is tiny enough to work with the pads on SMT components, and the iron itself is small enough that you can actually manipulate it like a pen or pencil - meaning you can be VERY precise). The ST50 is about $350 (with the TD100 iron; the tips you'll have to order separately). That's a significant investment, I know, but if you're going to do any kind of precision soldering (including things like re-soldering wires to DCC decoders when they break off), then it is definitely worth it. Like every other task, having the right tool is 90% of the battle, and the wrong tool makes the process impossible.
I do note that Ngineering sells a small 12w iron with a tiny tip for this kind of work. I haven't tried that, but I can tell you that if you try to do this with a Weller or Radio Shack iron - even their smallest ones - you'll end up disgusted and throwing nearby objects. I just got through soldering some 32-gauge magnet wire leads to two 603 LED's with the Pace, and the whole process took about three minutes (literally - I put a piece of double-sided tape down on my desk, laid out the LEDs upside down pressed to the tape, cut 4 pieces of magnet wire, turned on the Pace - which takes about 15 seconds to reach operating temperature BTW - tinned the magnet wire ends with a blob of solder on the Pace tip, cleaned the tip and then soldered the leads to the LEDs). There is no way on earth I could have done this with my 20w Weller, even with its smallest conical tip.
John C.