First total engine rebuild '96'RM 250

Well, I know it's an old engine but decided for the learning process, I would tear it down and rebuild bottom and top end after main bearing failure. I have it in pieces on my work bench. I will be replacing all bearings as some were a little questionable. Do I need to do the main needle bearing off of the crank? It seems fine but dont want to leave any stones unturned while im in there. If I do I guess someone will have to press the crank apart? Like I said just me and the service manual on re assembly! Hopefully not too bad though. any advice on a project like this?? She is older but I figure if I replace everything it will be like new!? We'll see how it goes? I'll post pics as I go.