"For starters, I'd like to access Captains House on GDPLAPTOP from TDPLAPTOP"
I'm assuming "Captains House" to be a sub-folder of C:, i.e. C:\Captains House. If it is not, replace it by the appropriate path.
Using TDPLAPTOP:
If you are not logged under Tim:
NET USE X: "\\GDPLAPTOP\C$\Captains House" <Password for Tim> /U:Tim /P:NO
If you are logged under Tim:
NET USE X: "\\GDPLAPTOP\C$\Captains House" /P:NO
Will map drive X: on TDPLAPTOP to C:\Captains House on GDPLAPTOP.
Type DIR X: or Use Explorer to open the new X: drive
Since both machines are laptop, if you connect wirelessly you'll have to ensure your W-Router allows wireless to wireless communication.
Using GDPLAPTOP you can remove Sharing from Captains House and you'll still be able to access it from TDPLAPTOP. And others won't. So you can open what you want to who you want.
Please try that and I'll call it a day.