Shaw won't do it, I called. they say they don't put two modem in one account and want to charge me for secondary account, which is double what I pay $60 x2.

Shaw rep says modem rental is different than Cable TV, which they can activate multiple. I don't know if that is bullshit or not.

No, you need two things for Amped setup. They can be either:

SR600EX(transmitter)+AP600EX(receiver)

Or

SR600EX(transmitter)+UA600EX(receiver)

Solution 1 gives you another wifi network at the receiving end while solution 2 gives you a USB access stick on the receiving end. (works if on 1 computer needs to be connected, of course you could buy multiple of them but that makes little sense)

What's wrong with running a 100' cat 6 ethernet cable to the guest house? Cat 6 cables should maintain a solid connection.

Regular ethernet cable is not designed to be exposed to elements. Not to mention how to do it nice and tidy so the installation doesn't bring more trouble down the road.

But I think you have a point. If OP is looking for a long term solution (plan to keep internet live in the guest house), laying down a few cat 6 actually make a lot of sense.

1000' outdoor cat6 (something nice allowing direct burial) should run no more than $200. Lay down 2~3 cables at once (so in case of one breaks, another can sub in quickly), put a good wi-fi AP at the guest house and voila.

Who do I call for such job? contractor? or electrician?

Usually all electrician would offer such service.

I wouldn't bother with special network installer/contractor for this job as it's relatively simple (unless you plan to wire the whole house with some fancy wired+wireless setup. That's another topic).

Call around for quotes and make sure they are an established entity+bonded/insured and you should be good to go.

I'm not sure how much would they charge, but for reference, my friend here in GTA got the whole house wired up for just over $1000. (materials included, full cat6)

Just remember to not cheap out of installation. True pros who really know what they are doing would save you a lot of trouble down the road.