The trick don't work in all the new vehicles they are putting starters in the gas tank. Stupid engineering.

Don't assume it's the starter, check the batteries voltage first, then check for corrosion at the terminals. Can't jump it if the insides of the terminals are crusty. And yes, the internet is the best place to buy car parts nowadays- usually about a third of what the local auto parts sell them for and they are coming from the same factories.

Buying online is fine unless you need to take the part back because it's the wrong part. I get our parts at the local parts store - you can look at the part in hand before you buy and try it.

I'm thinking you did not mean to say gas tank. There is no way that would work. Fuel pumps are now in the gas tank, but starters have to be able to rotate the engine. There are some that are placed internal to the engine in the intake manifold area.