OCR Science Controlled Assessment

Hey guys, I've been recently worrying a lot about my science coursework...I'm in year 10 right now, and have taken triple science, and I have a few questions I wanted to ask:

1. Honestly speaking, how hard is it? I'm honestly quite bad at practical experiments, and I still don't know how to use those cursed ammeters and voltmeters - I'm going to get some help from my teacher when we do some experiments related to them, but overall I'm still quite bad, so any advice on the difficulty of the coursework would be appreciated.

2. The coursework is 75% of the actual GCSE, which is quite a substantial figure - so how well would I need to actually do in the coursework to get an A*? Please take into account that I go to a grammar school, and that A*s in all sciences is almost compulsory.

3. Will we receive help from teachers? When will we get to know what the controlled assessment is based on?

Any additional information will also be appreciated. Thank you!