Calf Pain

Hi Coach,Can you help me out please.
I have been training for my first marathon and I have run into some problems.
I have excesive pain in the upper calf muscle on my left leg.
I did a little homework on the internet and found that the pain is at the Superior Tibiofibular Joint, if that helps any.
The guy I buy shoes from said, my left leg is slightly longer than my right.
He suggested that I use a shime in the heel of my right shoe to make up the difference.
He suggested using corrigated cardboard.
Whick was marginally effective at low milage to help a pain I was experiencing in the tendon that runs from my achilis tendon through the arch(this is not my concern at this time. it is just back ground), but now at 18 to 20 mile runs it is largly ineffective.
What do I do, the race is 1 month away? One other thing, I pronate.
Someone said an arch support in both shoes will prevent the fibula from being pushed up into the lateral tibula.
What do you think?
I’m trying to use medical terminology to help you help me.
I don’t have alot of time to play with options.Thanx, Ralph