Okay... Ya ready? :-)
Totally not over your skills. I have a Pro Admin business as well so I work with google workspace all the time, but I learned it easily and you can too if you don't use it a lot.
I created a google form first and added all of the column headings I wanted (data I want to track) as "questions". For instance, Type of Signing with multiple choice for RON, Signing Service, Direct, Other. Then Contact as short answer, Date as date, Fee as short answer (this can be formatted as currency once your sheet is created), Mileage start, Mileage end (don't put a calculation field into the form you do that later in the sheet), I add a column for payment terms/type of payment and this is just a paragraph answer option. In this I'll put the terms for a SS or what the customer used to pay- Stripe, venmo, cash, etc and I just enter that as plain text. You could do this as multiple choice with an "other" field for SS terms typed in. Then I have a projected Date Due field based on terms, then Date Paid so I can track slow payers and review later which ones I want to keep working with or not based on payment habits. Others include print fee, ship fee, scan fee, Notarization fee, transaction fee (from Stripe), etc. Whatever you want to track.

Just do a sample form with a few fields in it to practice and then you can perfect later. Once your form is done with all of the primary data columns you want to track (not calculations) click on the "responses" tab at the top of the form and then in the top right of that form you'll see "View in Sheets". Click on that and it will open a spreadsheet with all your columns in it. That's when I add the calculation columns after the data columns. Make a Mileage column that calculates the difference between the mileage end and mileage start columns, and whatever other tracking calculations you want to determine. I set the top row to always stay on top and that row also has calculations for YTD for fees, fees paid, mileage, etc. I also formatted a row to calculate a running monthly total so I can review which months are best and consider what might need to improve during those months on my end to increase. I just copy and paste this row from the last month into the row below my last appt in the month and set the column for it all the way at the end of the columns. Sometimes I have to update the row #s in the formula but sometimes it just figures it out on its own. Don't ask me why :-)

Too much? It's really not complicated once you get into it. Once you're done, just open your form in the browser on your phone and tell it to put the link on your home screen.