Did I ride too much?

So I rode all four days over the holiday. Thurs,Frid, Sat, Sun I think I did around 150 to 170 miles. I took Monday as a rest day. Tuesday I walked about 3 miles. Tuesday pm, my legs started to feel heavy. They still do. I was able to get in 40 minutes on my trainer today and then did lots of stretching.

I want to go a 70 mile ride Saturday, it is mostly flat. What can I do to recover quickly?

REST, and then try stretching, and a slow easy ride.

How much riding had you been doing before the weekend? If you regularly do 100 miles plus a week, then I'd suggest "active recovery" - easy spinning, stretching. If the weekend was a big jump in mileage for you, then perhaps more days off with only a day of the more active recovery riding before Saturday.