As others have said, start hiking now to be in shape for the big event. It sounds fun.

Make sure to avoid cotton clothing, if possible. Non-cotton clothing will dry much faster if wet. Cotton takes forever to dry.

With your gear, make sure you have a repair kit with needle & thread, safety pins, etc.

I'd suggest you carry a daypack that has an integral water bladder (like a camelbak) that carries at least two quarts/day. Inside that, besides the water, the list of gear should include:

<>First aid kit, including blister gear (moleskin, duck tape, needle, antibacterial cream, small packet of handwipes)
<>Rain Gear - poncho or breathable rain suit
<>Doug Ritter Pocket Survival Pak, supplimented with: mini-Bic lighter, Ritter Photon Freedom light, & Micropur tablets
<>Ritter full size or mini RSK - GREAT knife!!! Consider whether you'll need a can opener
<>Extra clothing to match minimum temperatures
<>Nalgene polybottle (the whiteish plastic), 1 quart widemouth - though your primary water is in the bladder, take a supplimental bottle along in case of bladder problems - you can fill the bottle with gear if space is needed.
<>Trail food - something that won't get messy
<>Sun protection - wide-brimmed hat w/ neckstrap, sunglasses, lip balm, sunscreen
<>Good compass - take a look at the Suunto M-3 with the Global needle - keep in mind that a compass with a standard needle will not work correctly in both Brazil and England.
<>Very good map of the hiking area - know how to use it with your compass. Mark your map with UTM coordincate grids.
<>Consider a GPS - my choice would be a Garmin Geko 201. My favorite related book is "GPS Land Navigation" by Michael Ferguson. The how to buy section is a bit dated, but the how-to descriptions are excellent. Learn how to use UTM coordinates. Bring extra batteries.
<>Insect Repellent w/ 25-50% DEET
<>Toilet paper roll stowed in plastic bag
<>2 Large Trash Bags - all sorts of uses, including picking up trash
<>Extra pair of wool hiking socks
<>Extra pair of non-cotton hiking sock liners
<>2 Bandannas, preferably brightly colored
<>Polycord or Paracord, 50 feet
<>LED Headlamp w/ extra batteries
<>Small camera w/ lots of film or lots of memory cards & batteries
<>Small binoculars
<>Heavy duty Space Blanket - many uses, but especially useful for sitting on when the ground is wet
<>Hiking Staff - consider a bamboo martial arts staff w/ an added rubber boot on one end - contact a local instructor for a source. They are strong, lightweight, and cheap.

If you were off-trail I might suggest a small shovel for digging cat holes, but I'll guess toilet facilities are provided on the trail.

Go get very good hiking boots (I prefer leather over Gortex/nylon), put some good waterproofing on them, and start ramping up your practice miles now!!