Personally i think modern tech looks out of place asking side mechanical buttons from the 1980s
I tried replacing the head unit with an old alpine i had, same era as the car and it just looked crap
But that's just me
Sounds normal to me. Ideally you need to change the oil a second time after a few hundred miles as only half the oil comes out when you drain it. An oil change may help the hard shift. Wile uou have the sump off, follow Henryb advice and...