We currently have 105 units and are using a variety of excel, google docs/sheets/calendars, apartments.com (ads and rent collection), docusign and QuickBooks online (which we would like to keep). 

Sadly, it’s sat on the market too long and I’m looking to get creative with bringing the attention of many buyers looking for a good deal on a property (online auction or something else with tons of attention??)

Check out other online guides available here: https://www.biggerpockets.com/guides3.

Unfortunately, ESA (Emotional Support Animal) letters are tricky, especially with how easy they are to get online.

I would recommend first, finding and joining at least one if not more local real estate investor (REIA) meetup groups (look on Facebook or Meetup or just search online) and try to attend as many as you can to network with local folks doing all different avenues of investing.

Build your knowledge base through books, podcasts, and online communities.

Is it customary that they have their process displayed online or in a pricing guide so I can shop around?

You can also check their reviews online at Google, Facebook, or Yelp.

Is there any online services/tools where I can do the above DIY?

The way I do it is go to the property records for the county online find the owner's info and then Google search their phone number.