After being away from new vegas for a while I decided that it might be fun to create an assassin with hardcoe mode on. I'm thinking of using sniper rifles, and silenced pistols, explosives (Mostly Mines) and melee for combat, and be very sneaky. I will probably need a good survival skill as well.

What I could use is some advice on a special layout, some recommended perks, and any advice for a first time hardcoe mode player.

look in the cheats and hints there's a guide there for hardcoe but pick a build and stick with it don't use more than one ammo type if you can and use a secondary unarmed or other weapons ammo is heavy a baseball bat can be your best friend

Just a quick note, if you plan on getting sneak kills at close range, don't use melee but instead use unarmed. Power Fists, Ballistic Fists, etc have a much high DAM than almost all melee weapons.

Nah, screw the stealthy-ness and go for a loud son-of-a-[censored] who rolls with shotguns and explosives. Who says an assassins have to be stealthy?

SPECIAL: Perception and Luck are very important for a Sniper, Agility for the sneaky type. You might want to spend your 5 addtional points there and into Intelligence of course.
I'd go with the following layout
Traits: Built to Destroy, raises your base critical chance by 3. No-brainer, take it.

SPECIAL
S 5 - enough. You can buy an implant later, and with 6 you can use everything a typical Sniper depends on. Also STR is the easiest stat to increase when necessary(Buffout, Alcohol, Brahmin and Bighorner Steaks, etc).
P 5 - enough, if you plan to have ED-E around, who will basically grant you a PER of around 15. With an implant you'll get it to 6, so you can acquire Better Criticals later. Otherwise consider putting more points into here. As a sniper, you want to detect your victim before it can detect you.
E 5 - you're a Sniper, no need for Implant GRX or an excessive amount of HP
C 5 - your companions can die in HC mode, so better don't make it a dump stat if you want them to have chance of survival
I 7 - the *always useful stat*. You want to have some skill points to spend when leveling.
A 6 - affects your sneaking, AP points, draw speed, etc.
L 7 - determines you crit ability, 1% base chance per point. Doesn't sound like much, but with the right multipliers it is.

Useful Perks for Snipers in particular

Finesse - raises your base crit chance by 5
Better Criticals - 50% more crit damage
Travel Light - allows you to run 10% faster when in light armor. As a sniper you want to avoid direct confrontation anyway, and these 10% make the difference between outrunning your enemies or not. Also, as you want to play as a sneaky type, you'll want to stick with light armor to avoid the sneak penalties for medium or heavy armor
Hand Loader - the recipes for handcrafted ammo are too powerful to pass. .308 JSP rounds in particular will be your friend
Chemist - doubles the duration of any consumable, food, healing items, Stealth Boys. No brainer
Light Touch - adds 5% to your crit chance when in light armor Vigilant Recycler - again, very powerful recipes, which will also lower the weight of energy ammo
Jury Rigging - very useful for all kinds of builds, being able to repair your Sniper Rifle with a Service Rifle doesn't hurt for sure.
Meltdown - take this, use a Gauss Rifle with Max Charge or Optimzed ammo, and aim at a pack of Deathclaws- Massive lulz guaranteed.

See the HC guide thread for the importance of the Survival skill.
Oh ,and one additional thing: When using healing items, be awaere that itmes of the same type do not stack. So, if your health is low, don't drink 10 Sarsaparillas at once. It won't get you anywhere.
However, different items DO stack. So taking a Stimpack, a, Sarsaparilla, a Healing Powder and a Bighorner Steak (just as an example) WILL grant you all of their effects. This is an important technique to keep you alive when badly hurt in an intense battle when you can't flee.

I am making my own hardcoe assassin character, and am already 40+ game hours into it. I would strongly suggest NOT taking small frame if you are going melee or unarmed! You might think that extra agility is godly, but from my own experience, my character is getting crippled not just every fight, but nearly every time she gets attacked! Running through Doctor's Bags & Hydra like mad, I can tell you, is not a fun thing. Thankfully I just got ED-E recently so hopefully he can do a bit of the fighting and keep me from hobbling around half dead all the time now. Good luck with your own character!