Hey,
Congrats on your purchase and getting ready to take your check ride. I have a 68 182 and I love it. Your time with an instructor can be a couple hours or more, depending on how you feel and your instructor feels. I also transitioned from a 172 and I'm a relatively new pilot with just a couple hundred hours.
A couple things in no particular order and some folks with more experience may want you to do different than what I'm suggesting which is cool. I bet your plane will also fly a little different than mine as I believe your horizontal stabilizer is not as wide as mine.
Get a checklist and use it
On your checklist black out all the speeds shown in knots if your air speed indicator is in mph
Get your checkout / training from an instructor with a lot of 182 time
You'll need to use a lot of right rudder when taking off and you can ease the power in
It will really climb compared to the 172, which is a blast
I like to climb out at 100 mph so I can see other traffic at uncontrolled airports. My DPE suggested this during my check ride.
I flight plan for 15 gallons per hour, as it's easy math and I plan to land with at least 15 gallons
I have bladder fuel tanks and I like to leave the plane with 60 gallons of gas after I fly as I've heard it's bad to leave bladders with little gas
Practice all types of flight, takeoffs & landings with your instructor
When I practice power on stalls I don't use full power as the plane will just keep going.
Practice slow flight (0,10 & 20 degrees of flaps) and just cruise around
Using the constant speed prop and cowl flaps will become 2nd nature
I have a printed list of V speeds taped onto my dash
Charlie-Gumps (carb heat, gas, cowl flaps, mixture, prop, seatbelts)
I say what I'm going to do out loud
I trim a lot and it makes my flying easier
I turn the DG to runway heading when you are taking off and landing
It feels good taking off with 10 degrees of flaps
keep the ball centered
Fly with other pilots in the right seat. You'll have fun, go to lots of fun places and learn stuff
Before entering the runway I clear final and clear the runway. I also say: Engine or airspeed problems on the ground pull power and stay on the ground, Engine problems below pattern altitude pitch for 80 and land straight ahead or off to the side, Engine problems at pattern altitude pitch for 80 and turn right or left back to the airport. ( Your best glide speed might be different than mine )
When I takeoff I say & check:
Heels on the floor
RPM's good
Oil pressure good
Airspeed alive
Keep it between my legs
We are airborne
When landing I was having problems with being too fast in the pattern, so I came up with power and speed settings for getting into and during all phases of the pattern. I also check and say "clear final, clear runway" during ever phase of the pattern.
A lot of times I'll come in with no flaps if there is a good cross wind, gusty conditions or high winds down the runway
Have a great time, be safe and you can always fly another day