Congrats on the tazz to BMW upgrade.
completely different cars in the way they look, drive and feel. I wish you all the best.
Take my advice, as a previous 318i owner.
Do a proper oil service including a desludge. doesnt matter the mileage. just do it as part of the preventive maintenance.
Please dont do the CSL front bumber thing. Rather do the MTechII front and rear bumpers. but when doing this dont forget to change the side skirts as the Mtech body kit includes different skirts from the exlusive pack. make your car look like an MSport or Individual. + you can still add CF splitters to the MtechII front bumper.
++ if youre making the exterior look like a MTech model, try to do a similar thingy to the inside. maybe add the faux CF on the trim panels. And if the budget can be stretched, source some sport seats for the front.
Also, my advice is to also stick to a max of 18" wheels. the 19s will fit and sure will look good, but considering that its a 318i, youre gonna lose power. The Power Steering systems are not the best in these cars. adding much bigger wheels than came standard on these cars might not be a good thing for the power steering system.
All the other upgrades are cool. Seeing as you want to do a CF wrap on the bonnet, it might also be cool to add CF Kidneys. you can contact Secondskynz from this forum regarding the bonnet wrap.
Please note that the above statements are just my personal opinion and dont have to be entertained in any way. Im just stating what i think will be best for you and your car.