Hi Pat. You have received good advice. I will just add my voice to the chorus.
You will indeed arrive in Heraklion on the ferry. There are pretty much hourly buses from Heraklion to Chania. It will be about a 2 hour trip. The bus depot is about a 10 minute walk after you depart the ferry terminal. Turn right out of the gate and even with luggage it is an easy walk.
In Chania I suggest you find a hotel in the old town within the city walls. Staying in old town is a real treat. You might want to find a hotel on or near Theotokopoulo Street. Its full of small hotels tavernas and shops. It is very close tot the old town harbour but just far enough away to be fairly quiet at night.
You can easily spend your first couple of days just wandering the old town and harbour.
There are several places you can visit from Chania by KTEL bus or excursion. Look for a bus to Balos and Gramvossa. You get a boat ride along the rugged coast, a ship wreck, pirate fortress and two great beaches on this excursion. We did it by KTEL bus but we almost missed the return bus because it did not return to the drop off point. There were about 20 of us waiting at the drop off. Perhaps an excursion may be better. Any travel agent in Chania can sell you an excursion. KTEL has a bus to the Botanical gardens which we really enjoyed. Elafonissi is also a really good beach which you can get to by KTEL bus or an excursion.
This year we discovered Wanderlust Tours. It is a small group Max 12 people and it has several unique tours available.
You will have to return to Heraklion for the ferry to syros so you might want to find a hotel near the ferry port. We have stayed at Kronos several times. Its close to the Center of the old town but has sea view rooms. You can walk to the ferry port from there which will be about a 15 to 20 minute walk.
Here are a few images
Theo Street https://www.flickr.com/photos/stanbr54/albums/72157632118491316/
/Gramovossia,Balos and Elafonissi https://www.flickr.com/photos/stanbr54/albums/72157698932695812
Chania 2024 https://www.flickr.com/photos/stanbr54/albums/72177720318408008/
Wanderlust tours Chania https://www.flickr.com/photos/stanbr54/albums/72177720318394812
I also would second the suggestions that you stay a few nights in Sougia. The bus ride is spectacular as you cross over the white mountains. You can also take the ferry along the south coast.
Ferry trip Libyan Sea https://www.flickr.com/photos/stanbr54/albums/72157653434073393
Samaria Gorge from the bottom https://www.flickr.com/photos/stanbr54/albums/72157670610409530
Crete Libyan Sea villages https://www.flickr.com/photos/stanbr54/albums/72157645487373222
Sougia https://www.flickr.com/photos/stanbr54/albums/72157696633322660/with/45364786821/