I agree the thumb safety will need to be replaced. I agree at this point the thumb safety can be a sacrificial part. But past that,I suggest we slow down. Have a cup of coffee.
Fitting a new safety is a job that a mortal human being can do,maybe. But I suggest having more than one safety to work with,a Kuhnhausen,and a mentor to coach you an check your work. Its not quite intuitive and it has to be right. Handed a partially assembled 1911 frame and a new safety ,most folks wont know where to look and what to see regarding what may need to be filed and how much.Thats OK. If you are going to build 1911 s,learn. If its a one time maintenance thing,thats what smiths are for.
Most folks should leave fitting a safety to a 1911 gunsmith. Which means most folks should not FUBAR the operation by driving the pin out with a punch.
The safety fits through a window in the frame that traps a detail of the safety to retain it in the frame. It only comes out when clocked in the right position.
Forcing it out with a hammer and punch will damage the frame.
The sear is also engaged with the safety.
If you are going to go to a gunsmith at all, don't complicate the job with DIY efforts. If you beat the safety out and free the slide.you might feel like a hero,but if you do damage that complicates the smiths job.what good have you done?
Removing the mainspring housing makes transport safer. Its a normal disassembly routine that does not require forcing parts. You will do no harm.
I defer to Scorch on not removing the firing pin.Rather than debate the details,as an inertial firing pin,removing the mainspring means the hammer isn't going to launch the firing pin.Is a moot point.
If you have confidence you can completely do the job.and you will not have to take a FUBAR'd shoebox full of 1911 basket case to your gunsmith,go ahead,have fun,get your Dremel and hammer out.
Your smith can get that safety out,no problem.I suggest you let him.
Ordinarily,if its in the correct position,the safety can be pulled out pinching the thumb shelf.The end of the pin that is part of the safety is domed and protrudes from the opposite side of the frame.Thumb pressure on the end of the pin should be sufficient.Given its damaged,maybe a light tapping with a plastic hammer will be necessary,but if you get it wrong you are driving steel through steel.
Once again,if you will still need to go to see the smith,what will removing the safety and freeing the slide accomplish? Let the smith see the "crime scene" intact. It tells a greater story,maybe root cause of the problem.