...if I sent the funds to the wrong address(my first transaction) can the person then access my coinbase account for future transactions when I have substantially more bitcoin in the future on there?...
No, he can't. It even requires some effort for him to figure out where those BTC came from in the first place. The most he can figure out is that the BTC came from Coinbase, nothing else.
BTW, how did you get the receiving address for the first transaction? Wasn't it from your own Core wallet?
Yeah all I did was select receive funds on Core, typed in the amount that I bought on coinbase; got the address it created and pasted that into the sending information on Coinbase. When I open up Bitcoin Core it still says I have 0.00000000000 BTC pending and available.