X5 problem with cold weather -Start shakes, misfires

[Whitecat]

Hello all, i'm new on this forum, just bought E53 4.4 (30days ago) and already in problem....bought the 2006 with 70miles really mint condition at a glance and garage inspection done (not the dealer)

Since 2 weeks, when i start the big cat i got multiple misfire and all the cockpit shaking bad. I live in Canada Quebec...and out warranty..

Long story short went to BM dealer and put the car on computor all 8 cylinder were problematic, use camera to look into cylinders/valve (not to sure i'm not an expert)...anyway BMW suggest to clean / lift change Valve And work on head enginent component etc....and....asking for $7k....Man i'm in shock and so disapointed about all this.

Now i've red a lot in this forum about this issue but the challenge is to get a solution and summary
From all the possibilities scenarios - After reading some post it appear that some have decided to live with it .. My question : what about not fixing ? When i re start everything back to normal....Is this will damage other elements (paid the truck $20k)

Tx