10k race one week prior to marathon

I guess the marathon is an A race for you. If you are use to racing often, I would not see any problem, recovering from that. The problem would be that it will affect some extra intensity training which should be on wednesday prior to your marathon.

From my experience I would suggest you to go for that 10k race, pacing it 10bpm below your target heart rate on 10k race. Tipically this is the training I do the week end prior to a marathon. It should be a 10k tempo training.

This will be my first real marathon and I want to perform well.  I trained for and ran one in June, but 3 days prior to the marathon I had leg issues that severly impacted my performance.  I finished, but it took two hours longer than it should have.

 I have run a few 10k races and yes, I would expect to be sore for a couple days after the 10k race.

Thanks for the replies.

I think you just answered your own question.   You've had faith in whatever plan you're using up to now.  It's too late to change plans, and you are almost definitely better off sticking with the plan to the end, and skipping the 10K, especially since apparently it will affect your training during the week leading up to the marathon.  (If it's some socially important reason to go, then run the 10K as if it were the first 6 miles of your training run that day, and just keep going, but don't race it if doing so is going to make you sore for a few days.)