Terbodude,
This is an easy diy project. Timing or pressure are not changed with this repair. We have replaced many o-rings without any problems. Remove the fuel lines, If the intake is removed this job is easier but it can be done, then using a special socket remove the pressure valve and replace the o-ring. All DIYers should purchase the repair cd. This programmed repair is explained in detail, job 07.1-8627 on the repair cd

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Paul