I would think it could handle 1/4" steel, no problem, thicker stuff with multiple passes. $1000 might not be too much if everything works as it should and doesn't have lots of hours run time on it. If the seller threw in the welding leads too it might help sweeten the deal some. These went for over $2000 new. Maybe take him to the seller and let the hubby look at it and decide if it's worth it , I know it's supposed to be a surprise , just don't tell him anything about it till he sees it. Then tell him if he wants it and it's worth it ,it's his. Or do like Broccolli 1 said on the Miller site, "get naked, give him a stack of $100 bills and show him a picture of it". That might be a better surprise birthday gift than the machine alone:drinkup:
If he ends up with this little jewel, get him signed up on these two sites, so he can learn stuff and share any projects he may be working on. If it don't run factory perfect new there are several guys on here that may be able to help him get it that way. But if it don't run exactlly like new it might be a reason to ask for a lower price, the saved $$$ might be enough to buy him a new welding hood to go with it.