Jacked69,

If I decipher your rant correctly you had a local hobby shop professionally assemble a Top Flite P51 ARF including the installation of a Saito 100, all of the electronics, adjust all of the control throws (including flaps, throttle linkage, retracts), cut out the cowl, test fly the plane, and make final trim adjustments with a two week turn around time for $300.
After the fact ... a different hobby shop said they would have done the job with next day delivery for $100.
Have I interpreted the fragments of your rant correctly ??

None of your posts in this thread have indicated that the original deal (that both you and the hobby shop agreed to) was changed (in fact you have avoided answering that question) so it appears the hobby shop provided the services they agreed to at the price you agreed to pay.
For this plane with everything setup and ready to fly I personally think $300 is more than fair to you.

Maybe the test flight was not spelled out as being part of the deal, but it seems reasonable for the hobby shop to do this for all of the reasons that have already been posted.

I know you are beginner and you have no concept of what is involved to get this plane (or any plane for that matter) ready to fly ... you should be very very grateful that you did not find the other place that allegedly would do it over night for $100 ... this would most definitely be a case of getting what you paid for.
No one in the hobby shop business that knows what they are doing would agree to put this plane together for $100, much less with next day delivery.
Just the fact that they offered to do it for that price and that schedule would tell anyone with any experience at all that they do not know what they are doing.

You asked ........ "What should I do?" .............and someone else said ..... "Pray that no one reads your post from your local area".

I think you might consider taking that under advisement.