The Maintenance Schedule that I am finding online is absolutely awful, without providing actual mileage for different services to be done. I'm being told to change the drive belt, transmission fluid change, and spark plugs. I'm around 100k miles. Is there some other reference to see when belts, water pumps, spark plugs etc should be changed? Also, the drive belt is not the timing belt correct? When is that supposed to be done?

 

The drive belt is the serpentine belt+idler because the RDX has a timing chain. You should come close to changing the timing chain (if ever) until +200,000-300,00 miles. Check this link out for M.I.D. maint for the RDX: Acura Maintenance Schedules | Acura Owners Site

I would also include:
- power steering fluid if never changed
- brake fluid if it has been +3 years
- inspect power steering pump and rack for leaks
- check battery cables for corrosion
- check trans/axle seals for leaks

 

That link you provided is exactly what I'm talking about being the problem, it has no mileage connected to the maintenance minder codes, and for drive belt it just says inspect, and never when it should actually be changed. Same with the spark plugs. I'm trying to buy all the parts up front and then have an independent shop make the replacement, besides the drive belt itself, you are stating the idler needs to be changed? If so, do you have the oem part number for the idler? Thanks!

 

The "4" service is a mileage service set around 105,000 miles (spark plugs, valve adjustment, serpentine belt, usually water pump, antifreeze) . The brake fluid change is by time every 3 years. And items like antifreeze can be by mileage like 105K or time of 7 years. If the RDX was purchased used and you don't know the full maintenance history, I would plan to change all fluids/filters and do the 105K service and start my maint log from there. It has just been fluid changes, engine/air filters, and tire balance/rotations following M.I.D. maint schedule since my 105K service (+150,000 miles now).

I don't know the part number for the OEM serpentine belt kit.