Check Everymac for your model:
OWC will have appropriate RAM:
And here's an SSD with an IDE adaptor:
https://eshop.macsales.com/item/OWC/SSDMXLE120/
Grab a PRAM battery. You'll definitely want to replace it while you're inside:
Novus three stage polish works great:
https://www.amazon.com/dp/B002UCYRZU?psc=1&ref=ppx_yo2ov_dt_b_product_details
Buuuuut you might not want to polish everything by hand. This drill attachment kit will let you get farther, faster, buffing out every last scratch:
https://www.amazon.com/dp/B002UCYS2C?psc=1&ref=ppx_yo2ov_dt_b_product_details
These dust-free paper towels are handy and the kit only has three. You can grab more:
https://www.amazon.com/dp/B07GMQHB1L?psc=1&ref=ppx_yo2ov_dt_b_product_details
It's also great to have microfiber towels in abundance for buffing, wiping, cleaning and drying:
If there are plastics that have yellowed or gone dingy, and dish soap won't restore them, you can use this peroxide creme developer from Sally Beauty, and some UV light (sun works great!) to clean them up. Apply a thin coat with a brush, set in the sun or under a UV lamp, and check every 40 minutes. Don't let the creme dry out or you'll get nasty streaking.
https://www.sallybeauty.com/hair-color/shop-all-hair-color/40-volume-creme-developer/SBS-760635.html