We did not use an agent and don't speak Spanish. All the people working the canal speak decent English. Between three boats we had enough long lines and substantial fenders. You want to go lock through in the middle of the lock and you will be rafted with other sailboats. Going from the Caribbean you start in the afternoon and spend the night tied to a giant mooring in Gatun Lake not far from first set of locks. So you will have line handlers for guests for the night. Find some friends to take.
Our cost was $800 for lockage (plus the security fee which you get back) + $100 for one of the advisors with a pick up truck to take the fenders and lines back to the start + $15 for a local Sim card and air time (we had an open phone). When we went back to help the people who helped us we had a taxi to the bus station in Panama City ($8) + a bus to Colon ($3) + a taxi to where we were meeting our rides ($1).
You can go to the marina and do all the preps from there. We anchored off the boat club (didn't really see any boats). They charge $5 a day to use their dinghy dock. We came to Colon on day 1, started the paperwork on day two, were measured on day three (you have to anchor in the small craft anchorage which apparently is not very safe at night. We paid the fee on day 4. You have to pay cash. I did not like the idea of telling the cab driver to take me to the bank where you pay, since that would be advertising that I had $1500 in cash in my pocket, so I asked him to take me to the Port Capitan's office which is across the street from the bank.
The we left Colon for Christmas in a nicer place and came back for our canal passage on january 3rd as I remember. It is not as expensive, complicated, or physically difficult as a lot of people say.
