[Required 60,000 services]

If you're willing to invest your time, labor and buy a minimal tool set, most of what the dealer recommends e.g. t.body and MAF cleaning for example are simple. You can do yourself. It is questionable whether you need a brake system flush, ATF fluid or cooling system fluid drain & replace, also tasks you could easily do on a Saturday afternoon.

Watch Scotty Kilmer and others on youtube for how too's and what should be done by the professionals.  FWIW dealers most always are more expensive than an independent – it's how they pay for their high overhead.

 

[1999 Avalon Service Manual]

Try: https://www.emanualonline.com/cars/toyota/avalon/1999-toyota-avalon-service-repair-manual-software-emo-48094.html?product_country=&product_id=&placement=&adtype=&keyword=1999 Toyota Avalon Service Manual&msclkid=7268e0345c191491ea2e8255854efe52&utm_source=bing&utm_medium=cpc&utm_campaign=**LP - NonTM - Auto - Year%2FMake%2FModel - Service - L-Z&utm_term=1999 Toyota Avalon Service Manual&utm_content=1999 Toyota Avalon Service Manual

['07 Av Ltd: ABS & BRAKE light comes on>AC won't cool/Temp gauge inop/electric fans inop]

Sounds like a intermittent ground fault.  1) Check, clean and tighten all grounding points; 2) If you don't have a scanner, your local auto parts store will probably run a free diagnostic scan that could pinpoint the problem; 3) – least desirable and most expensive: take it to your local Toyota dealer. They'll do steps 1 and 2 and charge you a small fortune - YMMV.

[Can’t Find Strut mount for rear tires]

Rear top strut mounts are hidden behind the rear seat. There are youtube videos demonstrating the R&R process.

[Burned Oil Smell in car]

Had the same issue. Probably the rear valve cover gasket is cracked/split. Oil spills down on the exhaust manifold. PIA to R&R. While you're in there R&R the sparkplugs w/ the recommended iridiums.

[Door locks]

On my 2003 Avalon you have to blip the remote's 'unlock' button two or three times to unlock the other doors.

[2109 Avalon Engine air filter]

Why not just check it periodically? Clean it or R&R if especially dirty.

[Possible to change Oil maintenance length?]

Follow the recommendation in the owner's manual.  As Admin points out, how your vehicle is used. Also Scotty Kilmer on youtube, he says 100,000 miles of highway is equivalent to 20,000 of stop 'n go in the city.

[How often should I be changing the oil and filter ?]

Check the owner's manual. If you don't have one, you can find a pdf version. Google is your friend.

But once a year should suffice given the low miles you're logging.

[95 Avalon electrical issues]

Get an Autool <https://www.amazon.com/AUTOOL-Multi-Function-Water-Temp-Malfunction-Test-Automotive/dp/B07L8RPLCG/ref=sr_1_2?crid=1W4069YHB4XOI&keywords=autool&qid=1577665471&s=automotive&sprefix=autool%2Celectronics%2C272&sr=1-2>

For a description and demonstration see Scotty Kilmer's video <https://www.amazon.com/AUTOOL-Multi-Function-Water-Temp-Malfunction-Test-Automotive/dp/B07L8RPLCG/ref=sr_1_2?crid=1W4069YHB4XOI&keywords=autool&qid=1577665471&s=automotive&sprefix=autool%2Celectronics%2C272&sr=1-2>   The relevant segment starts at 2'30".