What's up sideburn,
For replacement of your filament guide, makergear.com (sorry makerbot.com) sells individual parts of the acrylic piece for the plastruder. Go there and just order the piece you need. Under the section plastruder parts, filament guide, I believe is the #4 piece.
For your second issue, is it leaking out at the bottom of the insulator or the nozzle head? If its the insulator, make sure that the insulator is threaded in to a point where it's tight (don't over-tighten it though). And to be safe, you can add a pipe clamp (the ones where you can tighten with a screwdriver, not sure of the specific name) around that area just to make sure there is a good seal. If it is around the nozzle head. I would dissassemble your heat rod and slide an M5 nut down to where your nozzle sits and tighten it with a wrench, just to make sure there is a good seal. Remove the nut and reassemble.
Hope it works out! Lemme know what happens.
