ok to start with dont worry about all of the millions of details you can get stuck in with
counting calories is great but burning them is better :P
you have a good weight to start with for your height so i wouldnt even bother looking at the scales anymore
make obvious improvements to your diet, more veg, less processed foods, less coca cola etcetc
as for the exercise do something you enjoy, your home gym sounds great, so use it!
personally i like to start with my cardio, have a light jog or jump on that bike of yours and get your body nice and warm, get your heart rate up there and get a good sweat on
when ready move onto your weights, pick a few body parts as you have already and simply highlight them be sure not to work the agonist and antagonist on the same day as you will tire too much / it will effect your recover and the building of your muscle
for example dont work your biceps and triceps hard on the same day, working 1 also hits the other lightly
on a monday you could work your chest, shoulders and biceps with the weights, finish of with sets of situps etc to strengthen your midright, i really rate body weight exercises for your core
tuesday could then be your legs, work that butt, your quads and hamstrings and wednesday back to upper body but diff muscles and so on and so forth
above all enjoy it, everytime you come back see if you can improve little by little
on a final note, to see the definition in your abs and other muscles you need a low body fat % so keep that in mind
good diet
good sleep
good exercise
thats all you need
