Wow, it's pretty cool to see this thread alive again after all this time. Katie, I'm glad you started it back up because this kind of thing is always on my mind even though I've gone through quite a change up in my approach to fitness.

When I was weight training prior to my pregnancy (3 years ago) and working with a trainer, I actually did a 30-60 minute session (sometimes he'd work with me longer, though I paid for 30) just once a week. However, I'd go back 2 more times that week and repeat the things we worked on. It was like going to class and then doing homework. This way I was able to get tips and pointers over a longer period of time. It worked out really well.

As for how much you need to do and how you need to feel, I guess I've changed my mind over time with that. I'm currently in line with Mark Sisson (Primal Blueprint) -- which is also compatible with others like Schwarzbien -- who believes you shouldn't be killing yourself. He does believe in a nice combo of weight training and intervals, which is totally my thing too. I think Jcass is on the money about how much you can reap without being so sore.

Currently I can't afford the gym, let alone a PT. I don't have the time either as I'm caring for a toddler and an elderly Mom (with dementia). However, I have some free weights and some DVDs and some space in my bedroom. Plus I have my bodyweight. And I'm shooting for 2 times a week to do some resistance based workouts to protect my muscle as well as build it back up. I've been mixing it up using the footboard of my bed for angled push-ups and the couch for tricep dips. You name it. Back to basics for me. LOL We'll see how it works.

But the one thing I want to be sure to comment on for you, Katie, is the heavy weight thing. IMO the heavier you're able to go, the better. But feel free to mix it up and listen to your body. If you are extra tired or aren't feeling that strong, go lighter with more reps (like Jcass said). But if you're feeling strong, go heavier and just keep the reps to the point where your form stays good. You are right to be most concerned about form.

The most important thing for you is to keep from injury, so embrace the fact that you aren't feeling all that sore but at the same time do keep challenging yourself. Personally I don't see a need to do resistance training more than 3x/week when you're doing full body and for me the efficiency of that beats any other approach. However, if you want to split the body up and you can afford the time and sessions, go for it. Just remember to build in enough time to REST and let those muscles rebuild and renew.

I'm game to make this a new thread if you'd like. One of us could just copy/paste what's been said into a new post and we can take it from there...