There are models like the 649 and 60 which can either be had in 38 SPL or 357 Magnum. You won;t be able to load a 357 mag into the 38 special and close the chamber. The 357 magnum was a result of some gun nuts who kept uping the performance level of the 38 special in certain strong revolvers. It wouldn't be safe to produce these commercially, as they would surely end up in a weaker gun that couldn't withstand the higher pressures. That's when the 357 Magnum was born. It's the same bullet, and same case, except the 357 case is about 1/8" longer to preclude someone from chambering it into the wrong gun. You can, however, safely shoot 38 specials in your 357 magnum.
In pretty much the same fashion, the 44 Special and some ambitious handloaders gave birth to the legendary 44 Magnum. Ergo, you can also shoot 44 Specials in your 44 Magnum.
As for care of the wood grips, they really don't require much care, but you can clean them in the same manner you'd clean furniture, or any other wood object. If you're really anal about it, you can get a can of Renaissance wax and wax them. Keep oil off them.
Heck, put up some pics of them!
I like Smith and Colt revolvers. I know several others here who do as well.