Jayjay, I'm right there with you. I've got 51 lbs still to lose til I get to my goal weight. Slowly but surely getting there.
Yeah, I hate the changing needs thing too. For me, I am on a reduced calorie diet, which has worked well for me for about 2 years now. And on days of long rides, I do up the amount on that day, and just that day. For me, I eat abour 1300-1600 calories a day for average workout days (anything 2 hours or less in duration of mdoerate activity). ON long ride days, since they run about 5-6 horus, I take in around 2000 calories for that day.
For maintaining, it's about 1800 calories on a daily basis.

I dont do many prepared food either unless I'm in a hurry, I tend to cook things myself. Healthier for me and my family. I use sparkpeople to journal my food each day and my calories burned. They are free, though you do have to sign up. I only use it for the calculators though, cause they have been the most accurate for me. It's helped a lot.
You are about 5 lbs lighter than I am I see after reading further. A calorie book is great too, you can just look up the amount of calories in certain foods.

The basic forumla is to burn more calories than you use. The BMR and RMR tell you your metabolic rate so you know how many calories a day your body burns on average (which for most people of an average weight (meaning not obese), it's about 1200 calories for your every day bodily functions). So, you automatically burn that just living. Then your goal is to burn at least 500 additional calories a day for loss. So, say you east 1200-1400 calories a day (which is the average amount for those looking to lose weigh who are under 200 lbs for a female). You should burn 500 additional calories a day for weight loss.
Like I said earlier though, I eat at a higher amount as I find that leave me feeling hungry to be that low. If you have been eating 2500-3000 daily, you could safely start off at around 1600-1800 (which is where you are saying), and start losing weight as it will be less than your system is used to.

Sounds like a few of us have some weight loss goals, it's good to be in good company