If you can deal with the weight its great. If you cant, get it milled. Ive yet to see a marker that can actually top the viking(the vice comes close, but nothing tops it). The board choices are mediocre at best ill say, but raw performance its amazing.
To work on a viking for the most part, you need a cartridge tool. AKA uses a special socket to remove the lpr, ram, and the two other caps on the tubes. A solenoid can be changed using your generic tools, and is very easy to do. All you do is unplug it, unscrew it, and put a new one on, though there are two different types of solenoids available for vikings, and I believe that they use different mountings. The older is the mac noid, it is silver and larger than the Humphrey. These are slower, but are known for being smoother(though this is debatable).The other type is the newer Humphrey solenoid. These are faster than the macs, as well as use less battery power. A marker using mac noids can be milled for humphrey solenoids by destructive customs(i believe at least, i dont know). Though in honesty, you wont have to worry about solenoids ever.
The only upkeep id recommend is sending the marker in for a tune up at destructive customs every year or two. This ensures that the innards of the gun are all functional, all the o rings are nice, the lpr is set well etc. I dont know the cost for this off hand, but it isnt too high.
If you do end up purchasing a viking, be sure to order some AKA lube(
www.akalmp.com has it). If you buy it direct, expect to wait around a bit for it to arrive. Beyond that, any adjustment you will do that isnt changing a fireing mode is pretty stupid on your part, because once the gun shoots, it shoots.
Beyond that, for actual on field performance expect the gun to be freakishly fast, and get alot of questions.
It may have a bit more "kick" than a dm3, but what doesnt. Accuracywise is whats to be expected with any paintball marker around. With quality paint, you will be able to hit what your aiming for.