Should be fine the Grundfos. If tackling your self the most important bit is to ensure the physical dimensions are the same from inlet to oultlet so as to keep it a straight swap with no pipework alterations
Most Manufacturers tend to play Ball with each other re fitment. Just google the pdf files and check. I'm not a Plumber btw (Sparx & Air Con) but do get involved in a lot of FM jobs on commercial prop with involves stuff like this
Once you have shut the pump valves off, unscrew the middle of the pump to see if the water is still running. Don't take it for granted the pump valves will shut off 100%. Have a bowl and some old towels ready. May the force be with you
I was playing it down tbh, it's actually a mini Plant room! We're on a Daikin Air Source Heat Pump so there is quite a lot of kit in there tbh. We have 3 pumps as it's a 3 storey House so each floor has it's own pumped loop with a Stat on each floor. It got a bit outa hand tbh as it does when building ya own gaff!
If the big nuts each side of the pump seem stuck, use a hammer and big screw driver or sharp chisel to jar them loose, always works