For oil change - be a lot easier to run the car up some ramps. Cost would be similar to a 2 ton trolley jack. Good to hear you have some jackstands - don't forget to get wheels chocks or use some scrap lumber/bricks to put behind the requisite wheels.

That said - there are multiple jacking points on the car.

As indicated in the manual, there is one behind each wheel, on the body seam, you'll notice two notches cut out of the seam. That is a jacking point for the OEM scissor. You can jack the car up on those points, but a floor jack / trolley jack will tend to damage that seam area. Better to fabricate a custom jack plate or place the jack immediately next to the seam. Note that will will only lift up that corner of the car - great for working on that corner, can be a pain if you want to lift up the whole axle.

Owner's manual will also note two other points - the front tow clip and the rear suspension beam. On the front towing clip - the jack plate can be put directly under the "belly" of the tow clip - that will lift the front axle in the air. On the rear beam - just have to center the jack under the beam, again - it will lift that whole axle.

For oil changes - I found that the front tow point could be used, but the jack can get in the way of the oil change. Ramps are trivial to use in this case - but don't have the flexibility of the jack. Example, before, when I used a floor jack - I loosened the lugs prior to lifting that axle - that way I could change the oil / coolant / etc. while I pulled the wheels off to check the brakes / axles / steering. Now with the ramps - I just line them up with the wheels - drive up, change the oil, and be back down in 15 minutes or less. Before it was a 45 minute - hours sort of job. Sure it was more convenient to do all that work in one shot, but I found that I didn't really save much time doing that. With my schedule, with a 20 minute window - I could blast out an oil change pretty easily. Ramps were lighter to throw around as well.

Ramps are pretty safe - as long as the ground you put them on is solid. I've got some Rhino ramps myself - these are fibre reinforced plastic ramps vs the stamped steel variants. As long as the ground you place them on is more or less flat - that sort of ramp will work great. Place them on concrete or asphalt - don't try to use ramps/jacks on soil or grass. A 3 ton jack stand is plenty strong for this sort of use.

Yeah, wouldn't be a bad idea to see what fluid they put in so you can match it. I'd be curious to see what they used, as the Toyota spec'd fluid is not a synthetic ATF.

As for your 2007 - I'm surprise the dealership changed the oil that soon. That uses a synthetic ATF and even under some severe driving conditions - most have been getting 60K-90K miles easily out of that oil.

Pan drop and filter change won't hurt - up to you if you want to do it. With a pan drop - make sure you get the right gasket (look at your pan, count the number of bolt holes and basic shape of the pan - even the dealerships can get this wrong). Filter will look more like a metal mesh screen than an actually filter. Should have the gasket for the filter and drain plug as well. Pan bolts use threadlocking compound - have to reapply threadlock when you reassembly the transaxle. Gasket is held on with three? bolts - note the location of the bolts as they come out, as they are different size lengths. Don't forget to clean off the magnets in the bottom of the pan as well.

In my case, it is a little different, as I tow with my cars - hence my short oil change intervals on transaxles. Still, doesn't hurt to change the fluid sooner - as long as you are comfortable with the service interval - have the time to do the job and get the right materials.

As for fluids - depends on the car. Your 2005 Corolla uses Toyota Type T-IV AFT, conventional, highly friction modified ATF. The 2007 Camry uses Toyota Type WS AF, synthetic, low viscosity, long life fluid. They do make universal fluids - example Valvoline Maxlife ATF that spec'd to work with both Type T-IV and Type WS AFTs. I use them in my cars, but I know full well that they are "universal" fluids - they are markedly different in viscosity between the Toyota OEM fluids. One of those - probably be safe to run, but if stuff hits the wall - you'll be SOL on transaxle life. If you want to be absolutely safe - only buy the OEM fluids.

As for fluids types - you can use synthetic in place of conventional - as long as it meets the friction and lubrication needs.

The OEM transaxle pan on both your 2005 Corolla and 2007 Camry should be just a conventional gasket - not sealant, bolts get a dab of loctite or similar thread lock. The oil pan, on the other hand, uses sealant - no gasket, plus bolts. Filter and gaskets do sometimes come in a kit - but if you buy them from the dealership - all of them will be separate. Most of the time, you'll find the kits at other online and physical autoparts retailers. Lots of materials for gaskets - some are plain cork, some composite cork+rubber, some just rubber, some are more exotic composites. Bottom line, just make sure the gasket fits the transaxle and you should be OK.