A 357 is a great choice.
Beginners can learn to shoot well with soft recoiling 38s or you can go all the way up to some heavy 357 loads.
Not to mention revolvers aren't sensative to feeding like many autos can be.
IMO a GP-100 would be heavy and a little bulky for a carry gun. I have one and it's great at home or at the range, but I wouldn't want to tote that much weight.
Since you're a big guy you can probably carry one just fine...but a lightweight gun would still be more comfy.
An SP-101 would be a little less bulky than a GP, but still a little heavy (for me at least). Taurus makes a model 85 in steel that would be comparable to the SP-101 but cost quite a bit less.
I have a S&W 637, which is an airweight J frame. I use it as my primary concealed carry gun and it's very easy to conceal and is light enough to not be bothersome.
You might want to look into getting an Airweight or one of Taurus' Ultralites.
Don't let the S&W model numbers confuse you too much. In the small J frames you have 3 basic configurations; one with an exposed hammer (Chief's special), one with a shrouded hammer (bodyguard), and one that has a small hammer completely enclosed (centennial). Then they come in either steel, aluminum (airweight), or scandium. Figure out what you want then just browse their catalog to find the model that has those features.
There are many choices. I suggest you shoot a few different guns. Most gun shops won't mind if you stick it in your pants either. Even without a holster, sticking it in your pants would give you a pretty good idea how it will carry.
For most of us, the perfect house gun isn't the perfect carry gun. My 6" GP-100 is perfect as my house gun because it's a lot easier to shoot it more accurately than a J frame and the extra weight makes shooting full power 357 pretty easy. My 637 is my perfect carry gun because of the weight and it's not bulky. I don't shoot it as well as the GP though (I shoot it well enough to carry) and I would prefer spitting out a heavier bullet at faster velocity.
...maybe you should buy two revolvers
You could buy an all steel gun like a GP-100, learn to shoot it well, then buy a lightweight for a carry gun.
I forgot to add...If you get a lightweight revolver then you may want to go ahead and skip the 357 idea and just get a 38 +P because they will cost less.
Full 357 loads in a lightweight will be a handfull. You can also buy 38 +P loads that equal low recoil 357 loads.
If you're thinking about a light 357 then shoot one first unless you have money to burn.