Sorry to hear of your loss. You can do it yourself, I did my dad’s which was a little complicated and Mrs T did her mums which was a”small” estate, but as others say you have to put in a fair bit of work.
For the size of your mums estate the price quoted is pretty good tbf, as long as they’re not useless. Others charge a % of the estate.
Should have no problem selling a house in OH, as you say one of the better areas in town.