First Post, questions about brake booster

Hey everyone, been lurking in the shadows since last year but never needed to post. I came from a 07 tundra and decided to try a tacoma as the next truck. Its been a great truck. I've enjoyed learning about it on here.

My brake booster is going out. The pedal feels mushy and I can here it sucking air. I found the PDF's on how to test it. It holds air when you pump it up and the enigne is running but if you turn off the truck it loose preasure. The check valve is good.

The problem I'm having is finding a new one. I've been to all the big box stores (NAPA,Pep Boys, AutoZone) and they can't get one. They go thru a company called CarDone. I went to all their website links and no one has one because CarDone quit making them. I contacted CarDone and they said "sorry". I contacted Toyota and they want $600 and it has to be shipped from Japan.

I found only one in a junkyard. They say its good because they tested it before it was pulled from truck.

Is their a way I can bench test it before I install it on truck?

Do I need to disconnect the brake lines or can I just move the master cylinder out of the way to get to the booster?

05 Tacoma V6 without VSC

Thanks for any help.

PS. If you have VSC pray yours doesn't go out. Those are more outrageous.