Putting different materials through the same extruder shouldn't be a problem. You just need to make sure you flush it out at the melting temp for your highest temp rated material. Did that make sense? Lol. For example, when switching from ABS to PLA. I print my ABS around 230C and my PLA around 200C. Make sure you use 230C (or your particular ABS heat setting) to unload the ABS and to load the PLA and let it run for a tad to clear out the old material. This will make sure the material that was removed melts and gets flushed out. Then you can just set your temps as you normally would and print away.

What type of Nylon are you printing with? I know that plenty of people print with the stock setup with some of the Taulman filaments, for example. I think some of those can print at under 250C.

My suggestion to you would be to learn to print in PLA, then ABS, then jump to Nylon. You'll be able to print in PLA much quicker than you can in Nylon (or ABS for that matter) and you should really know how the machine works the way it came before modding it or you won't have anything to compare it to. Nylon is very temperamental compared to PLA or even ABS. It absorbs water from the air so many people actually bake the filament at super low temps in the oven for a couple hours before using. You also need to print a whole lot slower with it. You will get more out of your time with the printer and enjoy the hobby a lot more starting at step 1... PLA. But that is just my humble opinion