Bryan has some good suggestions, but some could use improvement.
First of all, forget situps AND crunches. Neither one is a particularly useful exercise. Situps mostly train hip flexor endurance and crunches are for bodybuilders who want to make their ab muscles bigger. As he said, training the belly muscles has little to do with losing fat there. The best way to train the abs is to train the entire trunk with a big, functional exercise like Squats. Aikido ukemi actually trains them quite well on its own.
As far as losing fat, all the suggestions are missing the simple facts you need to concentrate on. Losing fat is about burning more calories than you eat on a long-term basis. Period. You need to run a continuous calorie defecit and not cheat. The reason exercise is important is that without it, dieting alone will cause your metabolism to slow down to compensate and conserve fat, and if you choose the right exercise, it will speed it up and increase the defecit. Make no mistake though, dieting is the most important factor in losing weight. This means systematically reducing how much you eat and being hungry a lot of the time for a long time.
As far as exercise goes, the best fat-burner by far is High Intensity Interval Training: HIIT. It is a type of workout originally conceived based on speed skater training. Comparitively, if your purpose is strict fat burning, anything else is a waste of time and energy. I consider resistance training also a basic necessary supplement to Aikido, but for different reasons. You can read more about HIIT by finding my posts from a couple years ago. Plug "HIIT" into the forum search. Here's a little flyer I printed up on it: HIIT
I agree about the deep tissue massage for the effected area, but not so much about the precautionary medical stuff. In my state, physical therapists don't even make assessments, doctors do. Unless you go to a really good sports med doctor that has world class PT's, your money is likely to be wasted for a problem as minor as a torn muscle. Personal trainers are taugt to always recommend this to protect themselves from lawsuits. If you already do Aikido without crippling pain or cardiac/pulmonary incidents, you probably don't really need to be checked out by a doctor.
As for getting a personal trainer, this would be great in theory, but most of them are worthless and expensive. I got one of the least prestigious credentials before I knew squat without even studying. I also got one of the best, later, and it was hard, but it was all theoretical, with no hands-on. The only credentials that include real, useful hands-on are from USA Weightlifting, one of which I also have, but this is limited mostly ot Olympic Weightlifting training and technique. If all you end up doing is adding some simple HIIT to your training, you should be able to figure out how to do a few adequate activities on your own: jumping rope, stationary biking, and rowing machines are among the safest.