Possibly made a mistake? (Advice needed)

So my stepfather collects krieg currently, and is really enjoying it. He's got lots of infantry/cavalry from the battalion box and has a command squad and all sorts, all painted up and done but he was on about some tanks the other day. I bought a leman russ tank for his 50th birthday, and am unsure if this was a mistake as I know next to nothing about imperial guard (i play orkz or space marine, my brother plays nids.). The only reason i bought leman russ was because i thought it was closest in asthetic to krieg, but i have no idea if its good or if thats correct or if there is a upgrade spru that is regiment specific like with space marines, but i have 5 days and the reciept to correct it, so if there is a tank that matches the asthetic/is better with krieg rules could i have some suggestions?