Change your oil as recommended in the owner’s manual.
Nothing needs a flush unless it’s clogged, and even then… If you’re at the point of trying to flush out a clog you should be considering a rebuild/replacement.

At 100k you should service the following -

Spark plug replacement

Belt replacement (there are 3 belts - AC, Alternator, and power steering if not done previously with timing belt)

Brake fluid flush

Coolant flush

Steering fluid flush

Transmission fluid replacement

The timing belt should have been replaced at around 80k miles on the Accent. The timing belt is a critical component, if it breaks the engine cylinders will smash the valves and destroy the engine. If the timing belt has not been serviced, you should do it right away.

At the same time of the timing belt, you should do the following as it all needs to come apart anyway, and if one fails you do it all over again -

Water pump

AC idler pulley

Timing belt idler

Timing belt spring

Timing belt tensioner pulley

Things to consider -

Front struts and rear shocks. 100k on the little car is lot of work for them and they are well worn, even if not leaking or showing signs of it.

Never EVER flush the engine or transmission if you want them to go any further.

You actually want neither. Flushes can cause issues (although uncommon).

What you want is a transmission fluid change. You also need to be on top of your synthetic oil changes to try to make it prevent the Huyndai 4 cylinder failures.

Your at the do I drop 2k on a 4 k car.Oil changes and general maintenance. I gotthe2010 with a rattle in the engine for years.