There are three types of connectors. The 5.5lb one is standard in most Glock pistols, however the G34/G35 use the 3.5lb ones. There is also a third connector at 8lbs, it is an optional piece. They are marked as follows:
3.5lb (-)
5.5lb (no markings)
8lb (+)
New York trigger springs increase the trigger pull as well. The stock coil spring that comes standard in Glock pistols seems okay, but it leaves a bit to be desired. The NY trigger springs come in two weights, the NY1 is olive in color and the NY2 is orange. I believe they are 8 and 12lbs respectively when used with the standard connector.
Basically the NY triggers provide a bit more to the trigger pull, they are however much superior to the coil type springs as they offer a very consistant trigger pull. You can mix them up a bit, I use a 3.5lb connector with a NY1 spring in all my Glocks, it offers a 5-6lb trigger pull and is very crisp and offers the best feeling trigger wise.
Word to the wise, never use an 8lb connector with a NY2 spring, it will render your pistol inoperable.
For parts, try Glock Parts. They ship springs and connectors no problem to Canada and the service is great.
I have never liked the stock connector with the coil spring in my Glocks, the triggers seem creepy and not consistant, when upgraded with a 3.5 connector and the NY1 it is perfect. Try it with the NY2 as well, you might like it. All these parts are relatively cheap, although the 3.5lb connector is a bit pricey I seem to recall. Best bet, order some 3.5lb connectors and both the NY springs and see what you like best.
If you know your way around the Glock internals, it will take about one minute to field strip, break down, replace parts and put it back together. Real simple, the parts are easily installed.
Hope this helps.