Again, it's all in how maticulous and careful they are when they install them. If you just lay the gasket on the dowel, and slap the head on,,, you're doomed for failure. Although it's a pain in the butt, a proper install will take alot of time and tedious alignment, etc. I know that all shops get paid for doing high volume, ergo they usually are not willing to take the painstaking time it takes for this sort of job. I hang out at one of the premier local speed shops every Saturday, but I would not allow them to do this particular job for me, per seeing how they prepare things before assembling, as most shops operate this way. Time is money! I have always done my own, simply because I would have no-one else to blame if things fail. Although, I've always had the guidance of a friend who has taught me virtually everything I know, and I would trust him to perform brain surgery on me, (he's not a doctor.)
In the end, it's up to you, but you do need to have a great deal of trust in the guys doing it, and if I did not know them personally, I doubt I'd allow them to do it. This opinion is based on the fact you said you don't have access to credible shops such as Cotton's, Conley's etc. If it's a Buick based shop, then no problem,,, let em' do it. If it's someone that builds small block Chevy's all day, then you're taking a risk, IMO.
In the end, it's up to you, but you do need to have a great deal of trust in the guys doing it, and if I did not know them personally, I doubt I'd allow them to do it. This opinion is based on the fact you said you don't have access to credible shops such as Cotton's, Conley's etc. If it's a Buick based shop, then no problem,,, let em' do it. If it's someone that builds small block Chevy's all day, then you're taking a risk, IMO.