I want to replace my gate controller with Arduino and don't know what shields

I'm strong in mechanical design and basic electrical so I can understand somewhat but I'm a total new-b and have never touched or operated any type of Arduino so please be thorough with your explanations. Ok, the controller board on my security gate is junk but the 24vdc 15-20amp brushed motor, power supply, and limit switches are all good. I could just wire it up to a relay but I don't want 100% power to the motor on start up. It needs to ramp up so nothing gets broke. I want to use Arduino (or mega) to run a speed controller shield and listen to the limit switches as when to stop the motor. Also, activating the program will be from a simple momentary contact push button switch. If possible I'd like it to see a high amp draw from the speed controller to reverse motor in case of obstruction. I'll use a circuit breaker on the motor to stop any real damage to the motor or my vehicle. I need to know the complete list of what items to purchase to set it all up. I will use a laptop to load programming which I also need help with. I've only read about programming and don't know how to start or what to do to begin. Seems like it should be a fairly simple design and simple programming but you guys have done it all before and I need to learn from your experience. Once I have the working set up, I plan to use identical systems to automate two other processes on my farm.

I would buy a small dc motor and a small motor controller shield or breakout, and experiment with that to get used to it.

A 20 amp motor controller is not something you want to play with until you know what you are doing.

You can also test your limit switch scheme on your small-scale model.

Then get a motor controller for your actual motor. You want to get an over-rated one to reduce the chance of blowing it up.

Thank you for your idea and I agree I will definitely get it working on my bench with micro switches and play around with programming before installing it. I have some experience using pwm speed controllers (200A) that are Rc based but nothing microprocessor controlled. I'm thinking a Arduino Mega and the Megamoto are at least 2 of the items I need so far. Partly for their simplicity for connections.