Always worth doing yourself if you are physically capable.
I use a 12$ Extended Drain Filter by Mobil, and Toyota Genuine 0w20 Synthetic (Best oil for the price as per Bob is the Oil guy Forum) in my Mazda2. Total Cost about $40 for 4L oil with filter, and When I do it myself I use all 4 L of Oil. I will run this stuff about 12-15K kms or 1 year with no worries about extending the interval. Oil comes out very clean even after all those kilometers, if you aren't driving short trips and are driving in such a manner that gets you above typical MPG.
Reasons to D.I.Y.
1. It can be done in LESS time than it takes you to go to a dealership or quick lube place.
2.Your Drain bolt and doesn't get overtorqued (tightened) by minimum wage worker that barely knows how to turn a wrench, and you therefore wont have to repair or replace your oil pan.
3. You get more oil out on the change than a shop technician would, and you can fill to the proper level.
4. It costs less. No one does anything for free. If you can get it done for 40$ labour included, they are not using anymore than 20$ worth of materials, and will upsell you to death to make money.
5. You can monitor your engine's oil consumption better. My 2013 believe it or not was using oil when I decided to try Mobil 1 0w30. Doesn't burn a drop with the Toyota Oil.
Now, as far as cold or hot, I always do STONE cold, meaning I don't start the vehicle for at least 8hrs before draining, I always get a TON of old oil out. If you're doing it hot, its gotta be piping hot, and you've gotta wait for all the oil to drip down off of the valve train, which takes forever. Ambient temperature oil flows slowly, but it's all sitting in the lower part of the engine. If you lift the front end of the car you will get more oil out (hot or cold). Either way is fine, just don't run the vehicle for a few minutes before and expect it to drain properly, (worst is just moving the car just a bit before the drain).
As for relying on a pro to inspect things while under there, there isn't a whole lot that could go wrong that would fall under preventative maintenance, except for torn CV joint boots which can be replaced before you need expensive new CV Joints, have a look at them and if they are spraying grease everywhere, you need new ones. All other suspension/steering joints/bushings you should feel while driving before any novice technician is going to notice while under the car doing an oil change. As for brake inspections, when changing/ rotating wheels you can have a peek through the little window on the caliper to see how much Pad is left, if you have drums they rarely ever need servicing, you could have a more knowledgeable person help you inspect them. Any Oil leaks you may notice you would probably ignore if they are a slow leak since most oil leaks are very expensive to repair and require engine overhaul or transmission overhaul (usually game over on an old Mustachian Car)