#1 Priority - GFI Protection for this unit
#2 Priority - Unit that is rated for use above a shower
#3 Priority - Mounting, most cans have adjustable brackets for up to 24" joist centers, you will need an IC can for this type of mounting. What is the ceiling in the shower, drywall or is it a 3 piece fiberglass enclosure?

#1 - GFI protection is OPTIONAL for this light. It is NOT mandatory NO required.
I never GFI protect shower cans. There is no reason for it.

#2 - TRIM that is rated for use over a shower. The can is the same either way.

#3 - If the ceiling is up, as yours obviously is, you would use an "old work" can that just cuts into the sheetrock and is held up by clips. Using a new work can with the bars is useless and WAY more work than you want to know.

"#1 - GFI protection is OPTIONAL for this light. It is NOT mandatory NO required. I never GFI protect shower cans. There is no reason for it."

Doesn't it depend where the switch for the shower light is on the wall? In Canada if the switch is within 1m of the tub or shower the switch must be GFCI'd. If the switch is to be less than 0.5m from the tub/shower, it is just plain not allowed. What does the NEC about this?

A switch or receptacle cannot be withing the direct area of a shower or tub. Other than that all receptacles must be GFI protected and we must follow Mfg rules for things like bath fans, etc.
According to the NEC lights over tubs/showers do NOT require GFI protection unless the Mfg requires it. I have never seen a standard recessed can with a shower trim requiring this.

Ceiling is sheetrock.
Sounds like I need to exchange New Construction type Can fixture for Rework type fixture. I have plenty of accesible attic space and thought the new construction fixture would a better install but no need to reinvent the wheel. Amazing how much more expensive the Rework fixture is.
Appreciate your replies!

"Amazing how much more expensive the Rework fixture is. "

That should not be. Maybe a few bucks. What can did you buy?

New Construction Can at Lowes $5.86. Don't hold me to it but
I think the Rework was near $18.00.

Halo H7 series doesn't have that much disparity. I am curious as to what brand you bought.

If you have attic access from above a new work will go in fine.

Tony, do what petey racer says, #1, #2, and #3, and even #3 1/2 (ie, attic access available), unless you're nuts and really like attics. As to cost, I recollect that L/HD has some all-in-one remodel kits that include trim, and heck maybe flo bulbs too, for all I know - they cost more, but apples to apples, new const vs. remodel should be almost no difference in cost.

I purchased a Halo IC can. Most likely I was very mistaken concerning price of Rework Can. Will be checking it out probably on Monday.