I'm not sure why, but you will find MANY proponents of the "topsider" oil change method. This is the machine used by many to suck the oil out through the dipstick tube. The whole idea puzzles me, but as I say, you will get many replies to your post from people who swear by this system. I'm sure they get good engine life because they are, in deed, changing their oil.
The belly pan comes off very quickly and simply, by removing four screws. It's not a big problem. Draining the oil from the bottom, draining hot, and draining it for an extended period of time, will do a great job of cleaning the crankcase. I am convinced from checking several high mileage timing chains that fanatic oil changing, which keeps the microscopic particles drained out the engine, contributes to long timing chain life. As an added benefit, this will give you a chance to inspect things underneath that you would not otherwise see.
If you are not planning on keeping and driving the car for an extended period of time, you can get by with less thorough oil change methods with less frequency.
My personal oil change method consists of the following; roll in the garage on Friday night after work(95 mile trip which has engine warm) and trip the hood latch, go inside, change clothes, come back open hood, place drain pan underneath and pull plug, remove oil filter by catching spillage in container to keep engine compartment from becoming a mess, get up the next morning replace plug, install new filter and fill with oil.
Call me a fanatic or whatever you want, but the original engine in my 240D went 380K miles before overhaul with this method, and had the original timing chain in place at disassembly time.
By draining oil thoroughly and beginning with it hot, you will get more of the contaminates out of the engine because they are "churned up" in the oil.
Best of luck,
Change oil hot and change oil often,
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in