If you really don't feel safe working in the panel, install your ground
rods and the wire all the way back to the panel leaving plenty of extra
and then have an electrician stop by and make the connection in the
panel.

Pete C.

I am in COMPLETE agreement with this, and will add overall how old is
your main service?

dont patch something thats designed to last 50 or a 100 years do it
right once!