Hello, Unreal Engine 4 developer here, we have developed many games and apps in UE4 and are well versed in Blueprint scripting system.
Thanks for providing specific information regarding the work that needs to be done within your UE4 project, however we cannot provide a definitive quota on the project without discussing further regarding the state of your project is currently in.
We would love to discuss further regarding things such as -
1. Do you already have the rigged vehicles model ready that simply needs implementation in the game ?
2. The extent of the bugs regarding the Infantry units and the HUD widget.
Please get in touch with us so we can discus these in detail.