couple BHG q's

[twd420]

im a total newb to the BHG and just need to ask these to get my supra back on the road.

how necessary is it to machine the block and head when doing the HG repair?

when disconnecting the turbo piping to the air box i noticed the port was stained in what i think is oil. any insight to what that might be?

how do i check if there is any shaft play in the turbo, since thats one thing ive seen on here alot.

and is there any true benefits for 7mge cams into a 7mgte engine? i can get n/a cams for 75$, i only thought about using them since a couple lobes have rust spots on em.

any insight and help would be great, thnks