I've been lifting weights for several years, but have reached a point where I feel my workout is no longer gaining anything and I want to switch it up. My main concern is to get my body fat down and maintain size. Here is the workout I just started.

Workout 1 (Monday)

Barbell bench press
Barbell upright row
Dumbbell squat
Barbell bent-over row
Barbell curl
Dips
Barbell straight-leg deadlift
Shoulder press
Hanging leg raise
Front pulldown
Standing calf raise
Standing cable fly

Workout 2 (Wednesday)

Hyperextension
Seated calf raise
Dumbbell bent-over row
Leg raise
Dumbbell shoulder press
Leg press
Incline barbell press
Pull-up
Seated dumbbell curl
Dumbbell raise
Close grip bench press
Pec deck

Workout 3 (Friday)

Seated row
Decline barbell press
Hack squat
Dumbbell pullover
Cable pushdown
Dips
Dumbbell upright row
Preacher curl
Calf Press
Dumbbell deadlift
Arnold press
Crunches

Tuesday, Thursday, Saturday - an hour of cardio (treadmill or elliptical)

I don't know what I should use for sets/reps/weight for maximum gains. I started this routine a couple of weeks ago and walked away each day not feeling like I even worked out.

I was planning on using this for 8 weeks, then switching it up for another 8 weeks (something along the lines of a 'weighted' full body workout, where I would focus on 1-2 body parts while still doing 1 exercise for other parts) and then go to a split routine for 8 weeks and then come back to the full body, etc.

Any suggestions would be appreciated. Thanks.

Sh1t, all those lifts in one workout?

Too much?

I try to hit everything in my workout - chest, side delts, front delts, back, lats, biceps, triceps, quads, hams, calves and abs.

That was my first reaction too.

That is quite a bit my friend. Thing is you do have quite a bit of compund lifts which is very good! One down side about compound lifts is that they are hard and take a lot out of you when compaired to someone doing only iso and a few compounds.

If you can cut you routein down to say something like:
Bench
Row
Squat
Shoulder press
Pull-up
Chin-up
Lower back extention

and only do like one lift for each "catigory" and do it, and do it hard

What should I be doing in the way of number of sets/reps/weight? For example right now I am doing 4 sets, I start with the first set lighter and increase the weight while decreasing reps. The fourth set is usually close to my max weight for that exercise while doing 4-7 reps.

Why not Rippetoe's? Have you considered something like the following :-

Week 1:

Monday - Workout A
Wednesday -Workout B
Friday - Workout A

Week 2:

Monday - Workout B
Wednesday - Workout A
Friday - Workout B

Workout A
---------
Squat 5x5
Bench Press 5x5
Barbell Row 5x5
Dips 3xF

Workout B
---------
Squat 5x5
Standing military press 5x5
Bent Rows 5x5
Pull-ups/Chin-ups 3xF

OMG, I had a heart attack ustr eading all of those exercises....

I would recommend what the above poster suggested......select 3,4 or even 5 compounds max per workout and do a variety of rep set schemes. I like 5x5, 4x6 and 3x8. i even throw in 2x12 if I need to save some time.

Considering you have been working out for a couple of years I am sure I dont need to tell you that you dont need to isolate muscles to work them. Adding to that I think that isolation exercises are pointless in a cut.