The luggage issue is only really a concern when you have tight connections, any connection over 1 hour, or in your case, by busing to La Ceiba and then taking a ferry, you won't have an issue.
It's a common route for those with more time, you can see
Hedman Alas ::: Leaders & Innovators of land transportation in Central America Since 1952 ::: for their schedule and you can buy tickets on the day, most people that come to Utila for an extended stay take this option, I also use it myself from time to time.
As for costs on Utila, ball park, you're looking at $1 a beer, $150-200 to share a room in an apartment, or anything from $350 to $500 for your own apartment, there are numerous restaurants serving meals from $4-10.
There are paying DM jobs on the island, but you'll really need to be in the area for a while and know the sites and the creatures, most people that visit the islands just for diving, come for the small stuff, so you'll need good local knowledge and a trained eye before you can find paying DM work. I also did my DM on Koh Tao, and you get more experienced certified divers visiting the Bay Islands, so they have a higher expectation from there dives. Once you do get to know the sites, then you're looking at about $100-120 per week as a guide, plus tips, some DM's supplement this with extra work on the side. You'll make more as an Instructor, and I know most centers on Utila have been very busy so far this season, and there's a good chance of picking up work, and as an Instructor you'll make anything from $700 per month low season, to as much as $2000-3000 per month high season, again this all depends on yourself and which dive center you work for.
You'll find the diving more diverse, and exciting on Utila than Koh Tao, there are over 70 buoyed sites around the island, that get frequented daily, and most of the year. The Whale sharks are seen on the North side, and that's where the deeper walls are, and there's also offshore banks which are great for tec dives. I remember from Koh Tao there were bigger schools of fish but that was in 97, not sure what it's like today.
The atmosphere on the island is great as well, it's still got the charm a lot of places throughout the Caribbean have lost, there's no cruise ships coming in, no condominiums, there's relatively little traffic, and it's a lot of fun!
I hope this helps.
