The 5k health point boost is actually the only thing you will retain in PvP going from 49 to VR1. That is part of the Battle Spirit buff, that everyone gets.

If you want to know what you lose, leave Cyrodiil and note down all your stats (Health, Stamina, Magicka, Weapon Damage, Weapon Crit, Armor, Spell Resistance, Spell Damage, Spell Crit, Health/Magicka/Stamina Regeneration) from Character Screen.

Jump back in. What you have outside is what you will have inside after reaching VR1 (until the next major update hits, then you will lose this only upon reaching VR14). In Parts, that may already be higher than what you have inside, in parts it will be lower than that.

I will check this out when I get home . Never really played much attention to my stats but was you able to tell a big difference with the transition? I'm a Dragon knight imperial with almost all attributes to stamina and I run bow mainly with dualwield back up. I do really well in campaign and don't want that to change lol

It WILL change, significantly, if you have been playing on a non-veteran campaign so far. Veteran campaigns are... a completely different game.

EDIT: disregard that, just saw you play on thorn already.

The last time I made the switch from non vet to vet was maybe half a year ago on my sorc. At that time, we would get scaled to V1 not V12 as currently and I disabled the battle scaling around level 38 because my stats were better than the scaled ones.

I'd assume you 'd lose in the range of 1/3 of the pools for health and main resource (in your case stamina) and about 3/4 in your off resource (magicka for you). The regeneration stats should be much better, the other stats depend only on your equipment. I assume you could get away with little to no change on those, if your equipment is good.