Problems with PCM in 95 Lesabre??

We just bought this 95 Lesabre used for 5000.00. Had it for 3 weeks so far and now it is stalling. We took it for diagnostic testing (75.00) and they said the computer has to be replaced because it has a short in it. The car has 50k miles on it. We looked through all the paperwork and see that the PCM was replaced in 1999 at 35k miles. Is this normal? I am worried that we bought a lemon car. :(