Need advice
 

I recently bought A savage x ss the beginnning of july along with it i purchased a dx3s transmitter and some other hopups.
I had just about finished it when i encountered issues with assembly of the engine components throttle linkage and setting up and the transmitter and the sensors that come with it and was unable to finish it completely everything else was done.
So i had no choice other than to take it to the LHS so they could complete it because i am very new to the hobby i own 3 other rc's and all i am good at is engine maintenance
To put the story short they charged me $124.00 to finish where i had left off but did not install my RPM sensor correctly because it was defective, did a very poor job of setting the vehicle up, and they ran a tank of fuel through my engine without putting air filter oil in the filter and my fuel tank was contaminated with dirt.
I took my savage back to the LHS and discussed the issues and the offered to fix it free of charge but did not offer any sort of refund whatsoever.
Well i dropped off the truck 3 weeks ago and the only thing they are telling me is that they encountered a defective part and a new one is being back ordered which can take sometime.
Need some advice on this subject; should i ask for a refund or store credit ?
I don't think i am responsible in anyway for their mistakes.