Sir.
I will give you my opinion to your questions.
It is an old caliber, 100 plus years. Obsolete no. Has a good following among various shooters of various manufactures of revolvers.

Gun appears to be 25-5 from serial number. Yours would be from the 80's give or take a little. Model 25's from S&W have been around since 1955, and 45 Colt in a S&W goes back 100 plus years.

Grips appear to be S&W for a later model, those have some value do not give them away. If they fit your hand and style of shooting use them. There are others more correct for your gun. They would fit you differently.

500 for the package is bargain, most folks here would jump all over that.

You did good on the buying and have a gun that folks look for.
Bill@Yuma