I'm a mod of Enfield forums at Surplusrifle so allow me to shed some light.
1 - Absolutely yes ... No1's were used by the Australian forces right up into the Korean war. The No1 action is absolutely sound enough to do anything you want with it given the head space checks out and you have it stocked up and tuned correctly. Condition as with any rifle is the key.
1918 was a busy period for WW1 Enfield production ( BSA made just over 1 million rifles in 1918 ) so it won't be a low production year so you won't have to feel like you are using a safe Queen. They are still steeped with history however and are to be valued and looked after certainly - none of this however should prevent you from deploying yourself and it in the activity of hunting or target shooting. They are extremely hardy and parts can be replaced quite easily.
No1 rifles have been used to shoot 1000 yard Fullbore competition since before WW1 right up to this very day in Service rifle matches. These rifles ( and this action ) have also taken more of the worlds game than just about anything else out there as well as all of Africa's big 5.
2 - 1918 will be just fine ... get the gun smith to check head space most importantly. Everything else is standard for any other rifle, crown, throat, bore etc etc. I strongly recommend you visit the Enfield forum in my signature to get a much deeper understanding of the rifle and what they are capable of. You should be looking at a rifle that has matching serial numbers on bolt and receiver ( minimum ) ... Enfield rifles were always serial number matched at factory and are considered more valuable with matching numbers also.
3 - Ahhh yes ... I have restored a few and so have dozens of guys at the Enfield forums - like I said ... hit the link in my sig and you will get everything you need.
Bottom line ... if you do your part and make sure the rifle is clean and without damage to important working parts it will shoot better than you can.
Look forward to seeing you at the Enfield forum, post up pics and introduce yourself.
P.S Here is an example of what the .303 cal can do ... with a No5 Mk1 Enfield in the Aussie outback.