[RichardJ]

>> How do I fix the grinding into 1st? <<

When is it grinding? When you're down shifting ? I'll try again.

>>1st gear isn't synchronized, << YOU have to match the engine speed to the vehicle speed. Often referred to as double clutching.

Unless you're hauling a load, use 2nd, 3rd, and 4th, only, and the truck will do just fine.

Fill hole is on side of trans, driver side, 3 - 4" above bottom. Fill till oil runs back out.