Just me

Well, a couple of weeks ago, an Elliptical Trainer kicked my butt - Big time.  I jumped on, set the timer for 10 minutes and off I went.  Holy Man!!  I was tuckered within the first minute!  And the kicker was, when I stopped, so did the Timer... I didn't think that was very cool.
So, over the course of the last few days I've been able to eventually get to 5 minutes, but I hadn't been keeping track of how long it actually took me to get there, or how much I stopped.  Today, I set MY timer for 10 minutes and off I went.  I was able to go for 6 minutes and 40 seconds before my 10 minutes was up.  I figure thats not bad, tomorrow I will do 6 minutes, 50 seconds :)
I'm wondering if there is any significance to the order of my workout routine?  I haven't been for an assessment or met with a trainer - only my doctor.  She wanted me to walk 20 minutes one day and lift weights for 20 minutes the next and take one day off a week.  I've been pushing myself harder than that, trying to get a good 30 minutes in a day.
Today, I walked for 10 minutes getting m heart rate up to 140 or so.. then switched to the recumbant boke for another 10 minutes, (I try to get my arms moving with some light weights while on that thing) and then my 10 (6:40) minutes on the Elliptical Trainer, followed by another 10 of walking, gradually slowing as I go.
Hows that sound?
As I've got so much weight to lose I am worried about having a bunch of excess skin .. how do I prevent that? Arethere certain excerices I need to be doing?  I want to get rid of the flabby under upper arms and the belly fat, but have no idae what the proper 'moves' are.
Anyway, my day is almost done - I'll be back tomorrow!