When you say poor pressure do you mean that you have to press the pedal down further than you used to to get the same result? If so bleed the brakes. Gases are compresible, liquids arent.
As you say you are a noob.
Do this by starting at the caliper furthest from the servo, usually pass/rear. Get a suitabale bit of pipe that fits over the bleed nipple. Loosen the bleed nipple, get a mate to pump the brakes 10x on the last on hold the pedal to the floor. Tighten bleed nipple NB do not over tighten as you will knacker caliper/ break bleed nipple in caliper which is a PITA. Work you way round drivers/rear, pass/front, drivers/front etc making sure you do not let the fluid drop all the way down in the resevoir otherwise you'll suck air into the system, this is a bad thing.
Another point is to bed in brakes, I personally do this on my cars and hasn't failed me yet. This guide saves me typing it out...
HTH's
http://www.zeckhausen.com/bedding_in_brakes.htm
