Re: 'Sniperize' surplus rifles?
OP - if by "sniperizing" you mean heading off into the garage and slapping some sort of mount and a modern scope on any old dog of a milsurp, I think you'd be better off saving the money as others have said.
If you mean putting together an accurate repro of a classic rifle (Springfield, Enfield, Mauser, Moisin) then I can tell you it can be a very expensive proposition and finding the correct parts can be a long and frustrating experience....plus you need to start with the right rifle or you're just wasting time and money.
Chance are most people won't have the tools or engineering capability to do the job properly themselves and underestimate the work and cost involved.
Having said that, both the 70+ year old rifles I have had done are capable of 1 to 1.5 MOA accuracy and are great fun to shoot. so much so that I have a second Mauser K98k in the pipeline.....but they will never (in my hands at least) get close to a modern precision rifle.
Here's a link to a thread I ran a while ago, it also links into the homepage of the UK smith who did my Enfield No4T repro with an article on the work involved:
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2557323&page=1
boltstop's budget of around $2500 is reasonable....my Mauser cost about that that and the Enfield slightly more but they are both "period correct" and have period optics that were fully serviced (and in the case of the Zeiss rebuilt).
Right now a correct and original 98k sniper rifle is going to cost you well in excess of $10,000, a good correct and original Enfield No4T with all the CES will be $6,000 or more in the UK.
In the end it comes down to what your reasons are for doing it....if you want to get a sub-MOA tack driver for the fraction of the cost of a modern precsion rifle, you're probably going to be disappointed. If you want to have an interesting, practical and useable classic rifle that gives you a taste of old school precision marksmanship without risking a valuable and irreplaceable original, it can be a great project.