1. i did the 2-day hike w/ one night on the mountain via the standard "summit trail" which starts at the timpohon power station gate and ends at low's peak. also park regulations required to take a local park guide/insurance/permit w/ the sabah parks office which was about RM180/per person. my advice but, up to you is to definitely prearrange or book in advance your hut overnight beforehand with:
i saw a couple rollup without booked accomodations and got turned away since all the huts on the mountain were fully booked and they weren't issuing any additional permits for day. we booked our stay at the laban rata main hut but, turned out when we got there it was fully taken over my a bunch of organized tour groups so we had to stay a bit further up the mountain at the gunting lagadan hut. technically you could just hike up with water since there is a buffet plus snacks even sold in that main hut!
we also did the via ferrata circuit with:
it's done below the summit while not cheap it was awesome hanging off the side of the mountain,etc. i saw some great rock climbing routes they were developing so if you have the time and money i would take advantage. equipment i would definitely recommend are waterproof jacket/pants/hiking shoes since the skies opened up and dumped on us bigtime almost all the way down the mountain. also a warm light sleeping bag helps up on the mountain since you'll be starting from the humid jungle enviornment and feels a lot colder when your higher up. oh yes it was great hit'n the poring hot springs afterwards too.
2. the sepilok orangutan rehab center is a big tourist spot and photographer's dream. there are two feeding times a day and expect the masses. we missed the first in the morning but, there are other walking trails to checkout in the jungle. a very cool site on the viewing platform seeing the banana distributed amongst the large group of wild oranguatans--enjoy!