my kids are 10 months apart. i honestly don't find it hard at all. i would of had three under three last year but i had a miscarriage at 21 weeks. i'm not going to lie, they do fight. but most of the time they play together and have fun.
to answer your questions more specifically:
easy times/hard times: once they were both sleeping through it was quite easy for me. it's all about routine. it is hard having two sets of nappies to change etc but your 1st child may be out of them by then.
jealousy: it is normal for siblings to get jealous. they do it no matter the age gap. jealousy issues in my house are usually to do with toys or if one is sat on mummys knee and the other one wants to get on. they will usually cry and if they are really angry they might lash out at the other one. you have to learn to deal with that before a fight escalates
getting along: my two have similar intrerests in toys as the gap between their developmental age is lessening the older they are getting. they share toys (most of the time) they love to play hide and seek and play wrestling eachother.
sleeping schedules: to start with it's hard as the newborn wakes up but once my two were sleeping through it was easy. thy both go to bed at 8pm and wake up at 8am. they also both go down for an hours nap in the afternoon at the same time or if we are out they will fall asleep in their pushchair at the same time. they seem to be in sync with eachother
sharing room: this can be hard. one will inevitably disturb the other. usually to play or to annoy. this can mean it takes them longer to get to sleep or they may wake up earlier in the mornings. they will get out of it... eventually
hope i was of help.
if you need any more help feel free to pm me