new to tri not sure what to train for

Hey everyone. I am going to sign up for my first tri and I am having a hard time determining what level race to do and when to do it. I have been doing endurance sports for a few years. Most recently I was training (for the last year and 1/2) to do a 10 day 400 plus mile adventure race. I was doing 2-3 hours of training each week day and 4-6 hours each weekend day (approximately 20-25 hours per week). But about a month ago I went over the handlebars of my mountain bike and landed on my knee. I tore my ACL and need surgery. I will probably have surgery in the next month. Right now I am only allowed to ride the exercise bike (no mountain biking at all, but maybe road biking if it is a very flat course), aqua jog and swim. I cut down my training to closer to 10 hours a week until the surgery. I am not a very good swimmer. I had not been in a pool since I was six until last summer. I found out for my adventure race I had to be able to swim a mile and pass a swim test. So I started taking lessons and swimming 1-2 days a week. I am very slow but have signed up for another swim class. Based on my current fitness I would probably try to train for a 1/2 ironman or a full ironman for the end of the year. But I know that is not realistic due to the fact that I have to have surgery on my knee and will be out for at least a few weeks. Plus I have no idea how that will affect my overall fitness level. I just signed up for a sprint race at the end of August. I really need a goal as I am very depressed about missing my adventure race. And I need something to keep me focused on my rehabilitation. But I have no idea if that is realistic at all. I know everyone heals at different rates, but does anyone have any experience coming back from this type of surgery. I am think I can do the swim and the bike, but even a three mile run might be too much three months after surgery. Also even if I can do the race, I am rather concerned about cutoff times. I have never had to deal with cutoffs before. Some sprints don't give the cutoff times. Don't know if this means there are not any or they are standardized and I should know without being told. Any advice would be greatly appreciated.