Please help me with my tub and faucets!

[Mimi78]

I have purchased a whirlpool tub(american standard) and it says to set it in a bed of mortar or something, but the people at Home Depot told us to spray Great Stuff under it instead because it won't crack like a mortar would. Which should I do? Can I do either?

Also another stupid question, we have a three handle shower fixture and I would like to change it out to a two or single handle faucet. Are all faucets universal or do I have to have the pipes changed in order to accomodate a different type of fixture?

----What kind of mortar should I get exactly-I checked the manufacturer's instructions and they said IF I want to do so, I can use a bedding material, and it mentioned mortar. So do I really need the bedding and if so, what kind or type?

----Also a plumber came by and he said he has to install a shower tub fixture that is one handle because they are the kind that have a antiscald device in it and that there are no three handles that have that feature? Is this true, in that I have to change from the three handle to the single in order to have the antiscald device, which is required by code? The only reason I would prefer to keep the three handle config is because they look nice and I thought it might be less costly to just replace rather than having to do more extensive work to change out to a single. Maybe I'm wrong, but I am assuming it takes extra work to change it.