86 420sel timing chain

[bmb300sd]

I am replacing the timing chain, guide rails, tensioners and I few bent valves. The motor jumped time. I don't know any other details. I bought the car like that. I know the chain was replaced before but not the rails, thus the problem. I was wondering in removing the head I know I have to heli-coil the bolt holes, but I was told there a sort of "jig" I need to redrill the holes. Is this true? If so how do I get one? Also do I need to replace the head bolts to, do they stretch like on a Cadilliac Northstar? also I will order a new chain rails, and a head gasket set, is there anything I should look at replacing while doing this? or is there any other speical info I need to accomplish this task? I have done many timing chains and head gaskets before just never on an MB. Thank you for your time