1st thing 1st, go to your nearest auto store and purchase an oil suction/ sludge pump. it is a long tube shapped device with a pistion inside that is moved by a handle at one end with a long plastic suction tube on the other. (~300mmL and ~60mmW) this is essential if you want to get the oils back into your gearbox/ diffs!
Be aware that the transfer case uses different oil (trans fluid) so don't go draining that and thinking you can use the same stuff as the gearbox/ diffs.
The drain holes are all pretty easy to find on the lowerside/ edge of the box and diffs you will need a std 1/2 inch drive to fit the oil drain nuts. Obviously this is a lot easier to do if you have the car up on stands/ ramps. For the front diff, you may need to remove the front plastic apron for access. start at the front and work through to the back (order of draining the oils). once all the oil is drained, if find it useful to insert a piece of bent wire to fish out any loose solid objects (can also use magnet, but the openings are small), then attacha rag to your wire to mop up the remainder of the oil/ sludge (depending on how regularly the oils have been changed!!! ).
now is were you get that nice shiny oil pump dirty install the oil drain plug (sometimes I will allow some of the NEW oil to drain out, therefore removing any residual muck - so this is up to you), undo the oil fill plug (easy to locate on the diffs, I think the gearbox filler is about midway up on the right (drivers) side of the box from memory. suck up a pump full of the new oil - don't try to do it too quickly, as it will cause a spring effect due to the high viscosity of the oil and likely knock the container over LOL! once it is full, get back under the car and commence pushing the oil into the box/ diff. there are guides as to the levels required - I don't have the manual here at work... the diffs I generally fill to the point where it reaches the level of the filler hole. some boxes are huge and this method would take LOTS of oil (such as my tractor - but it needs that much!) so search for the correct amount, I tend to add a little extra (this is a cooling medium as well as lubricant!!!). install the filler plug and you are done
If you want to do the brakes, it can be a messy job (brake fuild is corrisive to paint!) and you WILL need a second person to 'pump' the pedal when bleeding air from the system - air in the system = poor performance, or worse, no brakes! most specialist brake places here in Aust only charge $55 to do a fuild swap/ flush which is good if you are not confident. However, being someone who likes to do these things myself ("if you want soemthing done right - do it yourself") it is a big job if you want to do it properly. I like to completly drain the system of current fluid (by opening the bleed screw closest to the master cylinder attaching a length of sutiable hose (put other end into a bottle or bucket - remember not to kick it - sending brake fluid all over your lovely duco once the master cylinder is drained (empty), lock off this bleed screw, then working from the next cloest to the farest open each in turn adn pump the brake pedal to expel old fluid. (remember to attach your hose). once this is all done, then you can fill the master cyl with the new fluid. open the screw that is FURTHEREST from the Master cyl and have your assistant slowly 'pump' the brake pedal until you see nice new fluid, repeat for remainder of each wheel, continuing with furtherest to closest... (so, are you sick of this yet or what!?!?!) Oh, and don't forget to continue topping up the master cyl!
now that you have new fluid showing at all the wheels, it is time to return to the left rear wheel (this being the furtherest from the master cyl) and bleed all AIR from the system. to do this, crack the bleed valve open about 1/4 - 1/2 turn and have your assistant depress the brake pedal - when the stream of fluid starts to deminish SHUT OFF THE BLEED SCREW! don't allow all the fluid to stop comming out before you close the screw, otherwise you are riskign air in the system. now that you have closed the screw, ask your assistant to remove their foot from the brake pedal (this is known as the "up" and "Down" shouts!) It takes some time, but persist and you will get there - your assistant will probably say that they are starting to feel pressure on the down stroke.
Ask your assistant to check the fluid level and fill if required (if they are not confident, best do it yourself! I've trained my wife to be very efficient at this job now, so she is a big help and doesn't spill a drop )
repeat the bleeding process moving from the furtherest wheel from the master cylinder to the closest. once you ahve done each wheel, give your aching back a break (no pun intended!) and now bleed the hicas - following the same procedure....
All things being equal, you should be able to do this easily and in less than 1 hr. test the brake pedal yourself, it should be firm and engage close to the top. start the car and check the pedal with the vacuum assistance, press hard - does it feel firm/ solid, does it creap towards the floor? any creap indicates a leak or air trapped... you know what that means - see above