As others have said, any reputable dive op won't take you to on difficult dives as long as you let the op know your experience level. With only 8 dives logged, going solo, diving in a new place, and probably new to drift diving it would be best to hire a private DM for at least your first day of diving or until you feel comfortable. I don't care how many dives someone has logged, every time one rolls or jumps off a boat somewhere they've never been they have a level of anxiety but that anxiety generally vanishes after a few minutes. If I were to guess after your first day with a private DM you probably won't feel the need for one the next day as you'll have a good feel for the drift, more confidence and less anxiety.
A private DM will cost you about $55 for the day (2 tank boat dive) and enjoying the luxury of a private DM is like enjoying the luxury of having a personal limo driver. Furthermore, personal DM's are really happy to land that job as it is so much easier than dealing with a group and they have time to really put their skills on display finding all kinds of cool critters just for you. I've personally been guilty of keeping an eye on people who hired a private DM as I like to see what their DM finds when he's on the hunt for critters (and generally hanging shallower with new divers) where we like to hang for photography as it's brighter and the color is so much better.
I'd also recommend a dive op that uses small boats 6-10 divers. Not a cattle boat op. Private DM or not it's best to be the newest diver in a small group of experienced divers than one in a group of 20 who plan to dive one day of their trip then rent dune buggies, swim with captive dolphins, go parasailing, followed by a day at the spa and then a tequila tour... Just my opinion. Also, when you no longer feel the need for a private DM, diving from a small boat will pretty much leave you with a personal DM as more experienced divers tend to like small groups and boats so they can venture out on their own a bit and dive their own profiles. That leaves you with pretty much a personal DM if you chose to hang close to him.
I've been diving Coz for 15 years now and have been diving with Tres Pelicanos the past 4 years. They certainly would be able to cater to your needs but as others have stated, there are several top quality dive ops in Cozumel that have virtual cult followings here. All would deliver great dive experiences. It's probably more of a matter of where you're staying and which one offers the most convenient pick-up/drop-off/transport.
I'll edit and add another comment to address your statement that you're not a strong swimmer. Well, no one is a strong swimmer loaded with dive gear! There is a reason DM's and captains tell divers before every dive, "Don't try to swim to the boat after surfacing - the boat will come to you". It is way easier to gently fin your way along underwater than to try and reach a boat after surfacing kicking away. One of the best things about Coz is the gentle current pretty much takes you on a tour all by itself with minimal effort... All you have to do is go along for the ride and if you see something cool you turn around and fin against the current it a bit.
