I agree with the others the guarantee was a little tight on time etc even with speedy delivery.
As for the reviews, you could take before and after photos to promote how good of a job you are doing etc and maybe ask if the person could leave you with a short review of how they felt the service was.
You could have a thread on here (you could use this one) and post the photos for all to see.
Also you should have photos of your connectors you have soldered and the electronics you have fitted, stuff like that will help.
best of luck