oil leak

Hi, i just bought a 1999 rm 250 at the begining of summer ive rode it a handfull of times and decided to change the oil in the transmission. i drained the old oil and put the correct amount of oil back in. I then took it for a spin and put it back in the garage. i come out the next day to a small puddle of oil under my bike. it never leaked before i changed the oil. After looking further i noticed that it is might be coming from the seal on the shift shaft or the seal on gear shaft. i dont know for sure though. There is also fair amount of grease\oil on my carb. i dont know if it is from chain lube or not. i was wondering how could i tell which one it is and how hard are they to replace..... or if it is coming from another place that i might be missing to see. any help of advice will be helpfull
thanks, Jordon

what should i use to pry out the seal in the manual for my bike it says to use a screw drive and pry it out along with removing the clutch and shifter shaft. i tried to work some on it tonight using a screw drive to pry on it but i didnt have much time cause i had to go to work. Is there an tips or suggestions to get the seal out or any special tool....also i noticed that a breather tube was plugged waith mud could that of been the reason that my sels are bad now