it may decrease gas milage
you cant
Warped rims or discs
It could be your rims are bent. Or it could be the rotors are warped
No, the only permanent repair for a blown head gasket is to replace the gasket. Anything else is just an emergency repair.
Be careful what people claim they can do. Alloy rims do not maintain strength when they bend and when you bend them back they become even weaker. Most reputable shops will not straighten alloy rims because of the potential for breakage and problems on the highway. Just find some replacment rims, you'll be safer.
Not usually. I've mounted quite a few tires, and had a few mishaps, but the rims never became warped or bent out of specification. Usually it takes a torch or a curb check to bend a rim.
Depends on who performs the repair. Also depends on if the head is cracked or warped. Get estimates from trusted shops.
Yes tires and rims are correlated based on the size of the tires you are looking for. While you can interchange rims and tires as long as they are the same size you will need to ask your mechanic or repair service center if you have an unusual size rim.
Depends, if only the gasket is blown. The head may be warped or cracked. Hard to give you a price because it also depends on where you live and who does the repair.
Brake cylinder repair is that wheel cylinder that holds the oil to keep your brakes running smooth on your back brakes. If you don't repair those you will mess up your rotors and your rims.
Depends on who performs the repair. Also depends on if the head is cracked or warped. Get estimates from trusted shops.