Well, I guess it all depends on your particular goals. IMO, if your short-term goal is to just "get in shape", then you probably don't need a personal trainer yet.
I have never had a personal trainer, and I am not knocking their effectiveness, and have at times considered hiring one because I thought they would be useful as a sort of motivator/coach (someone who would push me when I didn't really want to be exercising).
I then thought about what my goals were. Like you, I was really out of shape. Not particularly overweight, just not in the greatest shape due to many years of hard living (drinking, smoking, partying, etc.).
I'm still not in the best shape, but I think I am on my way. I tried the gym thing, but in my case I found that as soon as I paid the money, that pretty much guaranteed that I wouldn't go.
Eventually, I just began working out at home with some in-expensive equipment, such as grippers, chest expander, chin-up bar, stability ball, skipping rope, along with running and swimming.
At first, I didn't really have a routine. I installed the chin-up bar in the doorway that leads to my kitchen, and would do a couple of pull-ups every time I went into the kitchen. If I was watching TV, I would do some curls with the expander, or use the grippers. If I didn't feel like running, I would go to the parking lot and skip for 10-15 minutes. I still don't really have a routine, I just sorta work-out 4-5 times a day for short periods. Pretty much when I'm not really doing anything, I'll utilize that time by doing a few exercises.
I don't have a car, so I walk alot. I figured if I was walking anyhow, I might as well burn some extra calories by carrying some weight (I use a backpack with a bag of kitty-litter in it).
There are many, many ways you can slowly build up your level of fitness.
Again, I guess it really depends on your goals. At the moment, I have no goal to be a body-builder type, or get really big (I'm sort of short, and think I would look funny if I got really bulky).
Anyways, good luck, and congratulations of your decision to get healthy.