I just drive around the block for 10 minutes and use the 120F on the chart, fill to the middle of the safe zone. The safe zone, from what I've experienced gives you about 1/3 of a quart in either direction. You'd have to be foolishly way off your estimated trans fluid temperature to screw this up.
These dipsticks are avail on Ebay or elsewhere for less than $10 shipped. The cheap clone I ordered off Ebay is about 4 feet long which is rather cumbersome, but I suspect that's so it is compatible with other transmissions with MUCH longer dipstick tubes. After doing this a couple times, I've realized it's just as easy as any Hydramatic or other transmission that comes (or came) factory equipped with a dipstick. I agree the trans should come with a drain plug, but I fixed that problem by welding one in. I compare volume of fluid drained versus what is added to correct mark, and I've been spot on each time. I'm able to get about 5 to 6 quarts replaced with a pan drop & filter replacement.
Haven't heard anything bad about the 62TE, other than some shudder/torque converter problems when they were first introduced The trans itself is reputed to be pretty solid.