The best thing about a trainer is that you will be forced to work out, and can't use the 1000 excuses that we use every day. Is it expensive? Sure, a little. But what price do you put on your health and playing the best golf possible? I can think of so many worse ways that I waste my money...
I bet you can get a decent trainer for $50 an hour, maybe less if you go to their home. (If you go to a gym, it may cost more because the gym takes a piece...) If you can handle $100-150 per week and work out two or three time per week, I guarantee you will see the results.
The other thing about a trainer is that you will FINISH the routine. When I try to work out on my own, I stop about half way through because I feel like I have already had a good work out...The damn trainer makes me do the whole thing!
Once you decide to spring for the money and hire a trainer, the BIGGEST decision is do you go for the cute girl in tights or the muscled guy who kicks your ass! But that is a personal decision